4.5G 3.55-3.7 GHz band bulk acoustic wave resonator RF filter circuit

ABSTRACT

An RF circuit device using modified lattice, lattice, and ladder circuit topologies. The devices can include four resonator devices and four shunt resonator devices. In the ladder topology, the resonator devices are connected in series from an input port to an output port while shunt resonator devices are coupled the nodes between the resonator devices. In the lattice topology, a top and a bottom serial configurations each includes a pair of resonator devices that are coupled to differential input and output ports. A pair of shunt resonators is cross-coupled between each pair of a top serial configuration resonator and a bottom serial configuration resonator. The modified lattice topology adds baluns or inductor devices between top and bottom nodes of the top and bottom serial configurations of the lattice configuration. These topologies may be applied using single crystal or polycrystalline bulk acoustic wave (BAW) resonators.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority to and is a continuation-in-partapplication of U.S. patent application Ser. No. 16/019,267, titled “5.2GHz Wi-Fi ACOUSTIC WAVE RESONATOR RF FILTER CIRCUIT,” filed Jun. 26,2018; which is a continuation-in-part application of U.S. patentapplication Ser. No. 15/784,919, titled “PIEZOELECTRIC ACOUSTICRESONATOR MANUFACTURED WITH PIEZOELECTRIC THIN FILM TRANSFER PROCESS,”filed Oct. 16, 2017, now U.S. Pat. No. 10,355,659 on Jul. 16, 2019;which is a continuation-in-part application of U.S. patent applicationSer. No. 15/068,510, titled “METHOD OF MANUFACTURE FOR SINGLE CRYSTALACOUSTIC RESONATOR DEVICES USING MICRO-VIAS,” filed Mar. 11, 2016, nowU.S. Pat. No. 10,217,930 on Feb. 26, 2019. The present application alsoclaims priority to and is a continuation-in-part application of U.S.patent application Ser. No. 16/290,703, titled “5.5 GHz WI-FI 5GCOEXISTENCE ACOUSTIC WAVE RESONATOR RF FILTER CIRCUIT,” filed Mar. 1,2019; which is a continuation-in-part application of U.S. patentapplication Ser. No. 16/175,650, titled “5G BAND n79 ACOUSTIC WAVERESONATOR RF FILTER CIRCUIT,” filed Oct. 30, 2018; which is acontinuation-in-part application of the aforementioned U.S. patentapplication Ser. No. 16/019,267, filed Jun. 26, 2018. The presentapplication also incorporates by reference, for all purposes, thefollowing patent applications, all commonly owned: U.S. patentapplication Ser. No. 14/298,057, titled “RESONANCE CIRCUIT WITH A SINGLECRYSTAL CAPACITOR DIELECTRIC MATERIAL”, filed Jun. 6, 2014, now U.S.Pat. No. 9,673,384; U.S. patent application Ser. No. 14/298,076, titled“METHOD OF MANUFACTURE FOR SINGLE CRYSTAL CAPACITOR DIELECTRIC FOR ARESONANCE CIRCUIT”, filed Jun. 6, 2014, now U.S. Pat. No. 9,537,465;U.S. patent application Ser. No. 14/298,100, titled “INTEGRATED CIRCUITCONFIGURED WITH TWO OR MORE SINGLE CRYSTAL ACOUSTIC RESONATOR DEVICES”,filed Jun. 6, 2014, now U.S. Pat. No. 9,571,061; U.S. patent applicationSer. No. 14/341,314, titled “WAFER SCALE PACKAGING”, filed Jul. 25,2014, now U.S. Pat. No. 9,805,966; U.S. patent application Ser. No.14/449,001, titled “MOBILE COMMUNICATION DEVICE CONFIGURED WITH A SINGLECRYSTAL PIEZO RESONATOR STRUCTURE”, filed Jul. 31, 2014, now U.S. Pat.No. 9,716,581; and U.S. patent application Ser. No. 14/469,503, titled“MEMBRANE SUBSTRATE STRUCTURE FOR SINGLE CRYSTAL ACOUSTIC RESONATORDEVICE”, filed Aug. 26, 2014, now U.S. Pat. No. 9,917,568.

BACKGROUND OF THE INVENTION

The present invention relates generally to electronic devices. Moreparticularly, the present invention provides techniques related to amethod of manufacture and a structure for bulk acoustic wave resonatordevices, single crystal bulk acoustic wave resonator devices, singlecrystal filter and resonator devices, and the like. Merely by way ofexample, the invention has been applied to a single crystal resonatordevice for a communication device, mobile device, computing device,among others.

Mobile telecommunication devices have been successfully deployedworld-wide. Over a billion mobile devices, including cell phones andsmartphones, were manufactured in a single year and unit volumecontinues to increase year-over-year. With ramp of 4G/LTE in about 2012,and explosion of mobile data traffic, data rich content is driving thegrowth of the smartphone segment—which is expected to reach 2 B perannum within the next few years. Coexistence of new and legacy standardsand thirst for higher data rate requirements is driving RF complexity insmartphones. Unfortunately, limitations exist with conventional RFtechnology that is problematic, and may lead to drawbacks in the future.

With 4G LTE and 5G growing more popular by the day, wireless datacommunication demands high performance RF filters with frequenciesaround 5 GHz and higher. Bulk acoustic wave resonators (BAWR) usingcrystalline piezoelectric thin films are leading candidates for meetingsuch demands. Current BAWRs using polycrystalline piezoelectric thinfilms are adequate for bulk acoustic wave (BAW) filters operating atfrequencies ranging from 1 to 3 GHz; however, the quality of thepolycrystalline piezoelectric films degrades quickly as the thicknessesdecrease below around 0.5 um, which is required for resonators andfilters operating at frequencies around 5 GHz and above. Singlecrystalline or epitaxial piezoelectric thin films grown on compatiblecrystalline substrates exhibit good crystalline quality and highpiezoelectric performance even down to very thin thicknesses, e.g., 0.4um. Even so, there are challenges to using and transferring singlecrystal piezoelectric thin films in the manufacture of BAWR and BAWfilters.

From the above, it is seen that techniques for improving methods ofmanufacture and structures for acoustic resonator devices are highlydesirable.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to a method of manufacture andstructure for bulk acoustic wave resonator devices, single crystalresonator devices, single crystal filter and resonator devices, and thelike. Merely by way of example, the invention has been applied to asingle crystal resonator device for a communication device, mobiledevice, computing device, among others.

In an example, the present invention provides an RF filter circuitdevice in a ladder configuration. The device can include an input port,a first node coupled to the input port, a first resonator coupledbetween the first node and the input port. A second node is coupled tothe first node and a second resonator is coupled between the first nodeand the second node. A third node is coupled to the second node and athird resonator is coupled between the second node and the third node. Afourth node is coupled to the third node and a fourth resonator iscoupled between the third node and the output port. Further, an outputport is coupled to the fourth node. Those of ordinary skill in the artwill recognize other variations, modifications, and alternatives.

Each of the first, second, third, and fourth resonators can include acapacitor device. Each such capacitor device can include a substratemember, which has a cavity region and an upper surface region contiguouswith an opening in the first cavity region. Each capacitor device caninclude a bottom electrode within a portion of the cavity region and apiezoelectric material overlying the upper surface region and the bottomelectrode. Also, each capacitor device can include a top electrodeoverlying the single crystal material and the bottom electrode, as wellas an insulating material overlying the top electrode and configuredwith a thickness to tune the resonator. As used, the terms “top” and“bottom” are not terms in reference to a direction of gravity. Rather,these terms are used in reference to each other in context of thepresent device and related circuits. Those of ordinary skill in the artwould recognize other modifications, variations, and alternatives.

The device also includes a serial configuration includes the input port,the first node, the first resonator, the second node, the secondresonator, the third node, the third resonator, the fourth resonator,the fourth node, and the output port. A separate shunt configurationresonator is coupled to each of the first, second, third, fourth nodes.A parallel configuration includes the first, second, third, and fourthshunt configuration resonators. Further, a circuit response can beconfigured between the input port and the output port and configuredfrom the serial configuration and the parallel configuration to achievea transmission loss from a pass-band having a characteristic frequencycentered around 3.625 GHz and having a bandwidth from 3.55 GHz to 3.7GHz such that the characteristic frequency centered around 3.625 GHz istuned from a lower frequency ranging from about 2.9 GHz to 3.5 GHz.

In an example, the piezoelectric materials can include single crystalmaterials, polycrystalline materials, or combinations thereof and thelike. The piezoelectric materials can also include a substantiallysingle crystal material that exhibits certain polycrystalline qualities,i.e., an essentially single crystal material. In a specific example, thefirst, second, third, and fourth piezoelectric materials are eachessentially a single crystal aluminum nitride (AlN) bearing material oraluminum scandium nitride (AlScN) bearing material, a single crystalgallium nitride (GaN) bearing material or gallium aluminum nitride(GaAlN) bearing material, a magnesium hafnium aluminum nitride (MgHfAlN)material, or the like. In other specific examples, these piezoelectricmaterials each comprise a polycrystalline aluminum nitride (AlN) bearingmaterial or aluminum scandium nitride (AlScN) bearing material, or apolycrystalline gallium nitride (GaN) bearing material or galliumaluminum nitride (GaAlN) bearing material, a magnesium hafnium aluminumnitride (MgHfAlN) material, or the like. In other examples, thepiezoelectric materials can include aluminum gallium nitride(Al_(x)Ga_(1-x)N) material or an aluminum scandium nitride(Al_(x)Sc_(1-x)N) material characterized by a composition of 0≤X<1.0. Asdiscussed previously, the thicknesses of the piezoelectric materials canvary, and in some cases can be greater than 250 nm.

In a specific example, the serial configuration forms a resonanceprofile and an anti-resonance profile. The parallel configuration alsoforms a resonance profile and an anti-resonance profile. These profilesare such that the resonance profile from the serial configuration isoff-set with the anti-resonance profile of the parallel configuration toform the pass-band.

In a specific example, the pass-band is characterized by a band edge oneach side of the pass-band and having an amplitude difference rangingfrom 10 dB to 60 dB. The pass-band has a pair of band edges; each ofwhich has a transition region from the pass-band to a stop band suchthat the transition region is no greater than 250 MHz. In anotherexample, pass-band can include a pair of band edges and each of theseband edges can have a transition region from the pass-band to a stopband such that the transition region ranges from 5 MHz to 250 MHz.

In a specific example, each of the first, second, third, and fourthinsulating materials comprises a silicon nitride bearing material or anoxide bearing material configured with a silicon nitride material anoxide bearing material.

In a specific example, the present device can further include severalfeatures. The device can further include a rejection band rejectingsignals below 3.55 GHz and above 3.7 GHz. The device can further includean insertion loss of less than 2.5 dB and a maximum amplitude variationcharacterizing the pass-band of less than 1.5 dB. Also, the device canbe characterized by a 2F_(o) rejection of −50 dBc and a maximum averagegroup delay over the passband of about 40 ns. Also, the device caninclude a minimum attenuation of 40 dB for a frequency range of 700 MHzto 1000 MHz; a minimum attenuation of 45 dB for a frequency range of1900 MHz to 2400 MHz; a minimum attenuation of 50 dB for a frequencyrange of 2400 MHz to 2500 MHz; a minimum attenuation of 45 dB for afrequency range of 2500 MHz to 3340 MHz; a minimum attenuation of 40 dBfor a frequency range of 3340 MHz to 3450 MHz; a minimum attenuation of12 dB for a frequency range of 3450 MHz to 3530 MHz; a minimumattenuation of 12 dB for a frequency range of 3720 MHz to 3800 MHz; aminimum attenuation of 30 dB for a frequency range of 3800 MHz to 3910MHz; a minimum attenuation of 40 dB for a frequency range of 3910 MHz to4200 MHz; and a minimum attenuation of 50 dB for a frequency range of5100 MHz to 5900 MHz. The device can further include a minimum returnloss characterizing the pass-band of 10 dB and the device can beoperable from −40 Degrees Celsius to 85 Degrees Celsius. The device canfurther include a maximum power handling capability within the pass-bandof at least +27 dBm or 0.5 Watt. Further, the pass-band can beconfigured for 4.5G CBRS LTE applications.

In a specific example, the present device can be configured as a bulkacoustic wave (BAW) filter device. Each of the first, second, third, andfourth resonators can be a BAW resonator. Similarly, each of the first,second, third, and fourth shunt resonators can be BAW resonators. Thepresent device can further include one or more additional resonatordevices numbered from N to M, where N is four and M is twenty.Similarly, the present device can further include one or more additionalshunt resonator devices numbered from N to M, where N is four and M istwenty.

In an example, the present invention provides an RF circuit device in alattice configuration. The device can include a differential input port,a top serial configuration, a bottom serial configuration, a firstlattice configuration, a second lattice configuration, and adifferential output port. The top serial configuration can include afirst top node, a second top node, and a third top node. A first topresonator can be coupled between the first top node and the second topnode, while a second top resonator can be coupled between the second topnode and the third top node. Similarly, the bottom serial configurationcan include a first bottom node, a second bottom node, and a thirdbottom node. A first bottom resonator can be coupled between the firstbottom node and the second bottom node, while a second bottom resonatorcan be coupled between the second bottom node and the third bottom node.

In an example, the first lattice configuration includes a first shuntresonator cross-coupled with a second shunt resonator and coupledbetween the first top resonator of the top serial configuration and thefirst bottom resonator of the bottom serial configuration. Similarly,the second lattice configuration can include a first shunt resonatorcross-coupled with a second shunt resonator and coupled between thesecond top resonator of the top serial configuration and the secondbottom resonator of the bottom serial configuration. The top serialconfiguration and the bottom serial configuration can each be coupled toboth the differential input port and the differential output port.

In a specific example, the device further includes a first balun coupledto the differential input port and a second balun coupled to thedifferential output port. The device can further include an inductordevice coupled between the differential input and output ports. In aspecific example, the device can further include a first inductor devicecoupled between the first top node of the top serial configuration andthe first bottom node of the bottom serial configuration; a secondinductor device coupled between the second top node of the top serialconfiguration and the second bottom node of the bottom serialconfiguration; and a third inductor device coupled between the third topnode of the top serial configuration and the third bottom node of thebottom serial configuration.

One or more benefits are achieved over pre-existing techniques using theinvention. In particular, the present device can be manufactured in arelatively simple and cost effective manner while using conventionalmaterials and/or methods according to one of ordinary skill in the art.The present device provides an ultra-small form factor RF resonatorfilter with high rejection, high power rating, and low insertion loss.Such filters or resonators can be implemented in an RF filter device, anRF filter system, or the like. Depending upon the embodiment, one ormore of these benefits may be achieved.

A further understanding of the nature and advantages of the inventionmay be realized by reference to the latter portions of the specificationand attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the present invention, reference ismade to the accompanying drawings. Understanding that these drawings arenot to be considered limitations in the scope of the invention, thepresently described embodiments and the presently understood best modeof the invention are described with additional detail through use of theaccompanying drawings in which:

FIG. 1A is a simplified diagram illustrating an acoustic resonatordevice having topside interconnections according to an example of thepresent invention.

FIG. 1B is a simplified diagram illustrating an acoustic resonatordevice having bottom-side interconnections according to an example ofthe present invention.

FIG. 1C is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections accordingto an example of the present invention.

FIG. 1D is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections with ashared backside trench according to an example of the present invention.

FIGS. 2 and 3 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIG. 4A is a simplified diagram illustrating a step for a methodcreating a topside micro-trench according to an example of the presentinvention.

FIGS. 4B and 4C are simplified diagrams illustrating alternative methodsfor conducting the method step of forming a topside micro-trench asdescribed in FIG. 4A.

FIGS. 4D and 4E are simplified diagrams illustrating an alternativemethod for conducting the method step of forming a topside micro-trenchas described in FIG. 4A.

FIGS. 5 to 8 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIG. 9A is a simplified diagram illustrating a method step for formingbackside trenches according to an example of the present invention.

FIGS. 9B and 9C are simplified diagrams illustrating an alternativemethod for conducting the method step of forming backside trenches, asdescribed in FIG. 9A, and simultaneously singulating a seed substrateaccording to an embodiment of the present invention.

FIG. 10 is a simplified diagram illustrating a method step formingbackside metallization and electrical interconnections between top andbottom sides of a resonator according to an example of the presentinvention.

FIGS. 11A and 11B are simplified diagrams illustrating alternative stepsfor a method of manufacture for an acoustic resonator device accordingto an example of the present invention.

FIGS. 12A to 12E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device using a blind viainterposer according to an example of the present invention.

FIG. 13 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIGS. 14A to 14G are simplified diagrams illustrating method steps for acap wafer process for an acoustic resonator device according to anexample of the present invention.

FIGS. 15A-15E are simplified diagrams illustrating method steps formaking an acoustic resonator device with shared backside trench, whichcan be implemented in both interposer/cap and interposer free versions,according to examples of the present invention.

FIGS. 16A-16C through FIGS. 31A-31C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a transfer process using a sacrificiallayer for single crystal acoustic resonator devices according to anexample of the present invention.

FIGS. 32A-32C through FIGS. 46A-46C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a cavity bond transfer process for singlecrystal acoustic resonator devices according to an example of thepresent invention.

FIGS. 47A-47C though FIGS. 59A-59C are simplified diagrams illustratingvarious cross-sectional views of a single crystal acoustic resonatordevice and of method steps for a solidly mounted transfer process forsingle crystal acoustic resonator devices according to an example of thepresent invention.

FIG. 60 is a simplified diagram illustrating filter pass-bandrequirements in a radio frequency spectrum according to an example ofthe present invention.

FIG. 61 is a simplified diagram illustrating an overview of key marketsthat are applications for acoustic wave RF filters according to anexample of the present invention.

FIG. 62 is a simplified diagram illustrating application areas for3.55-3.7 GHz RF filters in mobile applications according to examples ofthe present invention.

FIGS. 63A-63C are simplified diagrams illustrating cross-sectional viewsof resonator devices according to various examples of the presentinvention.

FIGS. 64A-64C are simplified circuit diagrams illustratingrepresentative lattice and ladder configurations for acoustic filterdesigns according to examples of the present invention.

FIGS. 65A-65B are simplified diagrams illustrating packing approachesaccording to various examples of the present invention.

FIGS. 66A-66B are simplified diagrams illustrating packing approachesaccording to an example of the present invention.

FIG. 67 is a simplified circuit diagram illustrating a 2-port BAW RFfilter circuit according to an example of the present invention.

FIG. 68 is a simplified table of filter parameters according to anexample of the present invention.

FIGS. 69A and 69B are simplified graphs representing insertion loss overfrequency according to examples of the present invention.

FIG. 70 is a simplified diagram illustrating application areas for 5.2GHz RF filters in Tri-Band Wi-Fi radios according to examples of thepresent invention.

FIG. 71 is a simplified table of filter parameters according to anexample of the present invention.

FIG. 72 is a simplified graph representing insertion loss over frequencyaccording to an example of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to a method of manufacture andstructure for bulk acoustic wave resonator devices, single crystalresonator devices, single crystal filter and resonator devices, and thelike. Merely by way of example, the invention has been applied to asingle crystal resonator device for a communication device, mobiledevice, computing device, among others.

FIG. 1A is a simplified diagram illustrating an acoustic resonatordevice 101 having topside interconnections according to an example ofthe present invention. As shown, device 101 includes a thinned seedsubstrate 112 with an overlying single crystal piezoelectric layer 120,which has a micro-via 129. The micro-via 129 can include a topsidemicro-trench 121, a topside metal plug 146, a backside trench 114, and abackside metal plug 147. Although device 101 is depicted with a singlemicro-via 129, device 101 may have multiple micro-vias. A topside metalelectrode 130 is formed overlying the piezoelectric layer 120. A top capstructure is bonded to the piezoelectric layer 120. This top capstructure includes an interposer substrate 119 with one or morethrough-vias 151 that are connected to one or more top bond pads 143,one or more bond pads 144, and topside metal 145 with topside metal plug146. Solder balls 170 are electrically coupled to the one or more topbond pads 143.

The thinned substrate 112 has the first and second backside trenches113, 114. A backside metal electrode 131 is formed underlying a portionof the thinned seed substrate 112, the first backside trench 113, andthe topside metal electrode 130. The backside metal plug 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal 145. This backside metal plug147 is electrically coupled to the topside metal plug 146 and thebackside metal electrode 131. A backside cap structure 161 is bonded tothe thinned seed substrate 112, underlying the first and second backsidetrenches 113, 114. Further details relating to the method of manufactureof this device will be discussed starting from FIG. 2 .

FIG. 1B is a simplified diagram illustrating an acoustic resonatordevice 102 having backside interconnections according to an example ofthe present invention. As shown, device 101 includes a thinned seedsubstrate 112 with an overlying piezoelectric layer 120, which has amicro-via 129. The micro-via 129 can include a topside micro-trench 121,a topside metal plug 146, a backside trench 114, and a backside metalplug 147. Although device 102 is depicted with a single micro-via 129,device 102 may have multiple micro-vias. A topside metal electrode 130is formed overlying the piezoelectric layer 120. A top cap structure isbonded to the piezoelectric layer 120. This top cap structure 119includes bond pads which are connected to one or more bond pads 144 andtopside metal 145 on piezoelectric layer 120. The topside metal 145includes a topside metal plug 146.

The thinned substrate 112 has the first and second backside trenches113, 114. A backside metal electrode 131 is formed underlying a portionof the thinned seed substrate 112, the first backside trench 113, andthe topside metal electrode 130. A backside metal plug 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal plug 146. This backside metalplug 147 is electrically coupled to the topside metal plug 146. Abackside cap structure 162 is bonded to the thinned seed substrate 112,underlying the first and second backside trenches. One or more backsidebond pads (171, 172, 173) are formed within one or more portions of thebackside cap structure 162. Solder balls 170 are electrically coupled tothe one or more backside bond pads 171-173. Further details relating tothe method of manufacture of this device will be discussed starting fromFIG. 14A.

FIG. 1C is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections accordingto an example of the present invention. As shown, device 103 includes athinned seed substrate 112 with an overlying single crystalpiezoelectric layer 120, which has a micro-via 129. The micro-via 129can include a topside micro-trench 121, a topside metal plug 146, abackside trench 114, and a backside metal plug 147. Although device 103is depicted with a single micro-via 129, device 103 may have multiplemicro-vias. A topside metal electrode 130 is formed overlying thepiezoelectric layer 120. The thinned substrate 112 has the first andsecond backside trenches 113, 114. A backside metal electrode 131 isformed underlying a portion of the thinned seed substrate 112, the firstbackside trench 113, and the topside metal electrode 130. A backsidemetal plug 147 is formed underlying a portion of the thinned seedsubstrate 112, the second backside trench 114, and the topside metal145. This backside metal plug 147 is electrically coupled to the topsidemetal plug 146 and the backside metal electrode 131. Further detailsrelating to the method of manufacture of this device will be discussedstarting from FIG. 2 .

FIG. 1D is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections with ashared backside trench according to an example of the present invention.As shown, device 104 includes a thinned seed substrate 112 with anoverlying single crystal piezoelectric layer 120, which has a micro-via129. The micro-via 129 can include a topside micro-trench 121, a topsidemetal plug 146, and a backside metal 147. Although device 104 isdepicted with a single micro-via 129, device 104 may have multiplemicro-vias. A topside metal electrode 130 is formed overlying thepiezoelectric layer 120. The thinned substrate 112 has a first backsidetrench 113. A backside metal electrode 131 is formed underlying aportion of the thinned seed substrate 112, the first backside trench113, and the topside metal electrode 130. A backside metal 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal 145. This backside metal 147is electrically coupled to the topside metal plug 146 and the backsidemetal electrode 131. Further details relating to the method ofmanufacture of this device will be discussed starting from FIG. 2 .

FIGS. 2 and 3 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1A. FIG. 2 can represent a method step of providing a partiallyprocessed piezoelectric substrate. As shown, device 102 includes a seedsubstrate 110 with a piezoelectric layer 120 formed overlying. In aspecific example, the seed substrate can include silicon, siliconcarbide, aluminum oxide, or single crystal aluminum gallium nitridematerials, or the like. The piezoelectric layer 120 can include apiezoelectric single crystal layer or a thin film piezoelectric singlecrystal layer.

FIG. 3 can represent a method step of forming a top side metallizationor top resonator metal electrode 130. In a specific example, the topsidemetal electrode 130 can include a molybdenum, aluminum, ruthenium, ortitanium material, or the like and combinations thereof. This layer canbe deposited and patterned on top of the piezoelectric layer by alift-off process, a wet etching process, a dry etching process, a metalprinting process, a metal laminating process, or the like. The lift-offprocess can include a sequential process of lithographic patterning,metal deposition, and lift-off steps to produce the topside metal layer.The wet/dry etching processes can includes sequential processes of metaldeposition, lithographic patterning, metal deposition, and metal etchingsteps to produce the topside metal layer. Those of ordinary skill in theart will recognize other variations, modifications, and alternatives.

FIG. 4A is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 401 according to an exampleof the present invention. This figure can represent a method step offorming one or more topside micro-trenches 121 within a portion of thepiezoelectric layer 120. This topside micro-trench 121 can serve as themain interconnect junction between the top and bottom sides of theacoustic membrane, which will be developed in later method steps. In anexample, the topside micro-trench 121 is extends all the way through thepiezoelectric layer 120 and stops in the seed substrate 110. Thistopside micro-trench 121 can be formed through a dry etching process, alaser drilling process, or the like. FIGS. 4B and 4C describe theseoptions in more detail.

FIGS. 4B and 4C are simplified diagrams illustrating alternative methodsfor conducting the method step as described in FIG. 4A. As shown, FIG.4B represents a method step of using a laser drill, which can quicklyand accurately form the topside micro-trench 121 in the piezoelectriclayer 120. In an example, the laser drill can be used to form nominal 50um holes, or holes between 10 um and 500 um in diameter, through thepiezoelectric layer 120 and stop in the seed substrate 110 below theinterface between layers 120 and 110. A protective layer 122 can beformed overlying the piezoelectric layer 120 and the topside metalelectrode 130. This protective layer 122 can serve to protect the devicefrom laser debris and to provide a mask for the etching of the topsidemicro-via 121. In a specific example, the laser drill can be an 11 Whigh power diode-pumped UV laser, or the like. This mask 122 can besubsequently removed before proceeding to other steps. The mask may alsobe omitted from the laser drilling process, and air flow can be used toremove laser debris.

FIG. 4C can represent a method step of using a dry etching process toform the topside micro-trench 121 in the piezoelectric layer 120. Asshown, a lithographic masking layer 123 can be forming overlying thepiezoelectric layer 120 and the topside metal electrode 130. The topsidemicro-trench 121 can be formed by exposure to plasma, or the like.

FIGS. 4D and 4E are simplified diagrams illustrating an alternativemethod for conducting the method step as described in FIG. 4A. Thesefigures can represent the method step of manufacturing multiple acousticresonator devices simultaneously. In FIG. 4D, two devices are shown onDie #1 and Die #2, respectively. FIG. 4E shows the process of forming amicro-via 121 on each of these dies while also etching a scribe line 124or dicing line. In an example, the etching of the scribe line 124singulates and relieves stress in the piezoelectric single crystal layer120.

FIGS. 5 to 8 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. FIG. 5 can represent the method step of formingone or more bond pads 140 and forming a topside metal 141 electricallycoupled to at least one of the bond pads 140. The topside metal 141 caninclude a topside metal plug 146 formed within the topside micro-trench121. In a specific example, the topside metal plug 146 fills the topsidemicro-trench 121 to form a topside portion of a micro-via.

In an example, the bond pads 140 and the topside metal 141 can include agold material or other interconnect metal material depending upon theapplication of the device. These metal materials can be formed by alift-off process, a wet etching process, a dry etching process, ascreen-printing process, an electroplating process, a metal printingprocess, or the like. In a specific example, the deposited metalmaterials can also serve as bond pads for a cap structure, which will bedescribed below.

FIG. 6 can represent a method step for preparing the acoustic resonatordevice for bonding, which can be a hermetic bonding. As shown, a top capstructure is positioned above the partially processed acoustic resonatordevice as described in the previous figures. The top cap structure canbe formed using an interposer substrate 119 in two configurations: fullyprocessed interposer version 601 (through glass via) and partiallyprocessed interposer version 602 (blind via version). In the 601version, the interposer substrate 119 includes through-via structures151 that extend through the interposer substrate 119 and areelectrically coupled to bottom bond pads 142 and top bond pads 143. Inthe 602 version, the interposer substrate 119 includes blind viastructures 152 that only extend through a portion of the interposersubstrate 119 from the bottom side. These blind via structures 152 arealso electrically coupled to bottom bond pads 142. In a specificexample, the interposer substrate can include a silicon, glass,smart-glass, or other like material.

FIG. 7 can represent a method step of bonding the top cap structure tothe partially processed acoustic resonator device. As shown, theinterposer substrate 119 is bonded to the piezoelectric layer by thebond pads (140, 142) and the topside metal 141, which are now denoted asbond pad 144 and topside metal 145. This bonding process can be doneusing a compression bond method or the like. FIG. 8 can represent amethod step of thinning the seed substrate 110, which is now denoted asthinned seed substrate 111. This substrate thinning process can includegrinding and etching processes or the like. In a specific example, thisprocess can include a wafer backgrinding process followed by stressremoval, which can involve dry etching, CMP polishing, or annealingprocesses.

FIG. 9A is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 901 according to an exampleof the present invention. FIG. 9A can represent a method step forforming backside trenches 113 and 114 to allow access to thepiezoelectric layer from the backside of the thinned seed substrate 111.In an example, the first backside trench 113 can be formed within thethinned seed substrate 111 and underlying the topside metal electrode130. The second backside trench 114 can be formed within the thinnedseed substrate 111 and underlying the topside micro-trench 121 andtopside metal plug 146. This substrate is now denoted thinned substrate112. In a specific example, these trenches 113 and 114 can be formedusing deep reactive ion etching (DRIE) processes, Bosch processes, orthe like. The size, shape, and number of the trenches may vary with thedesign of the acoustic resonator device. In various examples, the firstbackside trench may be formed with a trench shape similar to a shape ofthe topside metal electrode or a shape of the backside metal electrode.The first backside trench may also be formed with a trench shape that isdifferent from both a shape of the topside metal electrode and thebackside metal electrode.

FIGS. 9B and 9C are simplified diagrams illustrating an alternativemethod for conducting the method step as described in FIG. 9A. LikeFIGS. 4D and 4E, these figures can represent the method step ofmanufacturing multiple acoustic resonator devices simultaneously. InFIG. 9B, two devices with cap structures are shown on Die #1 and Die #2,respectively. FIG. 9C shows the process of forming backside trenches(113, 114) on each of these dies while also etching a scribe line 115 ordicing line. In an example, the etching of the scribe line 115 providesan optional way to singulate the backside wafer 112.

FIG. 10 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 1000 according to anexample of the present invention. This figure can represent a methodstep of forming a backside metal electrode 131 and a backside metal plug147 within the backside trenches of the thinned seed substrate 112. Inan example, the backside metal electrode 131 can be formed underlyingone or more portions of the thinned substrate 112, within the firstbackside trench 113, and underlying the topside metal electrode 130.This process completes the resonator structure within the acousticresonator device. The backside metal plug 147 can be formed underlyingone or more portions of the thinned substrate 112, within the secondbackside trench 114, and underlying the topside micro-trench 121. Thebackside metal plug 147 can be electrically coupled to the topside metalplug 146 and the backside metal electrode 131. In a specific example,the backside metal electrode 130 can include a molybdenum, aluminum,ruthenium, or titanium material, or the like and combinations thereof.The backside metal plug can include a gold material, low resistivityinterconnect metals, electrode metals, or the like. These layers can bedeposited using the deposition methods described previously.

FIGS. 11A and 11B are simplified diagrams illustrating alternative stepsfor a method of manufacture for an acoustic resonator device accordingto an example of the present invention. These figures show methods ofbonding a backside cap structure underlying the thinned seed substrate112. In FIG. 11A, the backside cap structure is a dry film cap 161,which can include a permanent photo-imageable dry film such as a soldermask, polyimide, or the like. Bonding this cap structure can becost-effective and reliable, but may not produce a hermetic seal. InFIG. 11B, the backside cap structure is a substrate 162, which caninclude a silicon, glass, or other like material. Bonding this substratecan provide a hermetic seal, but may cost more and require additionalprocesses. Depending upon application, either of these backside capstructures can be bonded underlying the first and second backside vias.

FIGS. 12A to 12E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. More specifically, these figures describeadditional steps for processing the blind via interposer “602” versionof the top cap structure. FIG. 12A shows an acoustic resonator device1201 with blind vias 152 in the top cap structure. In FIG. 12B, theinterposer substrate 119 is thinned, which forms a thinned interposersubstrate 118, to expose the blind vias 152. This thinning process canbe a combination of a grinding process and etching process as describedfor the thinning of the seed substrate. In FIG. 12C, a redistributionlayer (RDL) process and metallization process can be applied to createtop cap bond pads 160 that are formed overlying the blind vias 152 andare electrically coupled to the blind vias 152. As shown in FIG. 12D, aball grid array (BGA) process can be applied to form solder balls 170overlying and electrically coupled to the top cap bond pads 160. Thisprocess leaves the acoustic resonator device ready for wire bonding 171,as shown in FIG. 12E.

FIG. 13 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. As shown, device 1300 includes two fullyprocessed acoustic resonator devices that are ready to singulation tocreate separate devices. In an example, the die singulation process canbe done using a wafer dicing saw process, a laser cut singulationprocess, or other processes and combinations thereof.

FIGS. 14A to 14G are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1B. The method for this example of an acoustic resonator can go throughsimilar steps as described in FIGS. 1-5 . FIG. 14A shows where thismethod differs from that described previously. Here, the top capstructure substrate 119 and only includes one layer of metallizationwith one or more bottom bond pads 142. Compared to FIG. 6 , there are novia structures in the top cap structure because the interconnectionswill be formed on the bottom side of the acoustic resonator device.

FIGS. 14B to 14F depict method steps similar to those described in thefirst process flow. FIG. 14B can represent a method step of bonding thetop cap structure to the piezoelectric layer 120 through the bond pads(140, 142) and the topside metal 141, now denoted as bond pads 144 andtopside metal 145 with topside metal plug 146. FIG. 14C can represent amethod step of thinning the seed substrate 110, which forms a thinnedseed substrate 111, similar to that described in FIG. 8 . FIG. 14D canrepresent a method step of forming first and second backside trenches,similar to that described in FIG. 9A. FIG. 14E can represent a methodstep of forming a backside metal electrode 131 and a backside metal plug147, similar to that described in FIG. 10 . FIG. 14F can represent amethod step of bonding a backside cap structure 162, similar to thatdescribed in FIGS. 11A and 11B.

FIG. 14G shows another step that differs from the previously describedprocess flow. Here, the backside bond pads 171, 172, and 173 are formedwithin the backside cap structure 162. In an example, these backsidebond pads 171-173 can be formed through a masking, etching, and metaldeposition processes similar to those used to form the other metalmaterials. A BGA process can be applied to form solder balls 170 incontact with these backside bond pads 171-173, which prepares theacoustic resonator device 1407 for wire bonding.

FIGS. 15A to 15E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1B. The method for this example can go through similar steps asdescribed in FIG. 1-5 . FIG. 15A shows where this method differs fromthat described previously. A temporary carrier 218 with a layer oftemporary adhesive 217 is attached to the substrate. In a specificexample, the temporary carrier 218 can include a glass wafer, a siliconwafer, or other wafer and the like.

FIGS. 15B to 15F depict method steps similar to those described in thefirst process flow. FIG. 15B can represent a method step of thinning theseed substrate 110, which forms a thinned substrate 111, similar to thatdescribed in FIG. 8 . In a specific example, the thinning of the seedsubstrate 110 can include a back side grinding process followed by astress removal process. The stress removal process can include a dryetch, a Chemical Mechanical Planarization (CMP), and annealingprocesses.

FIG. 15C can represent a method step of forming a shared backside trench113, similar to the techniques described in FIG. 9A. The main differenceis that the shared backside trench is configured underlying both topsidemetal electrode 130, topside micro-trench 121, and topside metal plug146. In an example, the shared backside trench 113 is a backsideresonator cavity that can vary in size, shape (all possible geometricshapes), and side wall profile (tapered convex, tapered concave, orright angle). In a specific example, the forming of the shared backsidetrench 113 can include a litho-etch process, which can include aback-to-front alignment and dry etch of the backside substrate 111. Thepiezoelectric layer 120 can serve as an etch stop layer for the formingof the shared backside trench 113.

FIG. 15D can represent a method step of forming a backside metalelectrode 131 and a backside metal 147, similar to that described inFIG. 10 . In an example, the forming of the backside metal electrode 131can include a deposition and patterning of metal materials within theshared backside trench 113. Here, the backside metal 131 serves as anelectrode and the backside plug/connect metal 147 within the micro-via121. The thickness, shape, and type of metal can vary as a function ofthe resonator/filter design. As an example, the backside electrode 131and via plug metal 147 can be different metals. In a specific example,these backside metals 131, 147 can either be deposited and patterned onthe surface of the piezoelectric layer 120 or rerouted to the backsideof the substrate 112. In an example, the backside metal electrode may bepatterned such that it is configured within the boundaries of the sharedbackside trench such that the backside metal electrode does not come incontact with one or more side-walls of the seed substrate created duringthe forming of the shared backside trench.

FIG. 15E can represent a method step of bonding a backside cap structure162, similar to that described in FIGS. 11A and 11B, following ade-bonding of the temporary carrier 218 and cleaning of the topside ofthe device to remove the temporary adhesive 217. Those of ordinary skillin the art will recognize other variations, modifications, andalternatives of the methods steps described previously.

As used herein, the term “substrate” can mean the bulk substrate or caninclude overlying growth structures such as an aluminum, gallium, orternary compound of aluminum and gallium and nitrogen containingepitaxial region, or functional regions, combinations, and the like.

One or more benefits are achieved over pre-existing techniques using theinvention. In particular, the present device can be manufactured in arelatively simple and cost effective manner while using conventionalmaterials and/or methods according to one of ordinary skill in the art.Using the present method, one can create a reliable single crystal basedacoustic resonator using multiple ways of three-dimensional stackingthrough a wafer level process. Such filters or resonators can beimplemented in an RF filter device, an RF filter system, or the like.Depending upon the embodiment, one or more of these benefits may beachieved. Of course, there can be other variations, modifications, andalternatives.

With 4G LTE and 5G growing more popular by the day, wireless datacommunication demands high performance RF filters with frequenciesaround 5 GHz and higher. Bulk acoustic wave resonators (BAWR), widelyused in such filters operating at frequencies around 3 GHz and lower,are leading candidates for meeting such demands. Current bulk acousticwave resonators use polycrystalline piezoelectric AlN thin films whereeach grain's c-axis is aligned perpendicular to the film's surface toallow high piezoelectric performance whereas the grains' a- or b-axisare randomly distributed. This peculiar grain distribution works wellwhen the piezoelectric film's thickness is around 1 um and above, whichis the perfect thickness for bulk acoustic wave (BAW) filters operatingat frequencies ranging from 1 to 3 GHz. However, the quality of thepolycrystalline piezoelectric films degrades quickly as the thicknessesdecrease below around 0.5 um, which is required for resonators andfilters operating at frequencies around 5 GHz and above.

Single crystalline or epitaxial piezoelectric thin films grown oncompatible crystalline substrates exhibit good crystalline quality andhigh piezoelectric performance even down to very thin thicknesses, e.g.,0.4 um. The present invention provides manufacturing processes andstructures for high quality bulk acoustic wave resonators with singlecrystalline or epitaxial piezoelectric thin films for high frequency BAWfilter applications.

BAWRs require a piezoelectric material, e.g., AlN, in crystalline form,i.e., polycrystalline or single crystalline. The quality of the filmheavy depends on the chemical, crystalline, or topographical quality ofthe layer on which the film is grown. In conventional BAWR processes(including film bulk acoustic resonator (FBAR) or solidly mountedresonator (SMR) geometry), the piezoelectric film is grown on apatterned bottom electrode, which is usually made of molybdenum (Mo),tungsten (W), or ruthenium (Ru). The surface geometry of the patternedbottom electrode significantly influences the crystalline orientationand crystalline quality of the piezoelectric film, requiring complicatedmodification of the structure.

Thus, the present invention uses single crystalline piezoelectric filmsand thin film transfer processes to produce a BAWR with enhancedultimate quality factor and electro-mechanical coupling for RF filters.Such methods and structures facilitate methods of manufacturing andstructures for RF filters using single crystalline or epitaxialpiezoelectric films to meet the growing demands of contemporary datacommunication.

In an example, the present invention provides transfer structures andprocesses for acoustic resonator devices, which provides a flat,high-quality, single-crystal piezoelectric film for superior acousticwave control and high Q in high frequency. As described above,polycrystalline piezoelectric layers limit Q in high frequency. Also,growing epitaxial piezoelectric layers on patterned electrodes affectsthe crystalline orientation of the piezoelectric layer, which limits theability to have tight boundary control of the resulting resonators.Embodiments of the present invention, as further described below, canovercome these limitations and exhibit improved performance andcost-efficiency.

FIGS. 16A-16C through FIGS. 31A-31C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure with asacrificial layer. In these figure series described below, the “A”figures show simplified diagrams illustrating top cross-sectional viewsof single crystal resonator devices according to various embodiments ofthe present invention. The “B” figures show simplified diagramsillustrating lengthwise cross-sectional views of the same devices in the“A” figures. Similarly, the “C” figures show simplified diagramsillustrating widthwise cross-sectional views of the same devices in the“A” figures. In some cases, certain features are omitted to highlightother features and the relationships between such features. Those ofordinary skill in the art will recognize variations, modifications, andalternatives to the examples shown in these figure series.

FIGS. 16A-16C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a piezoelectric film 1620 overlying a growth substrate 1610. Inan example, the growth substrate 1610 can include silicon (S), siliconcarbide (SiC), or other like materials. The piezoelectric film 1620 canbe an epitaxial film including aluminum nitride (AlN), gallium nitride(GaN), or other like materials. Additionally, this piezoelectricsubstrate can be subjected to a thickness trim.

FIGS. 17A-17C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first electrode 1710 overlying the surface region of thepiezoelectric film 1620. In an example, the first electrode 1710 caninclude molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials. In a specific example, the first electrode 1710 can besubjected to a dry etch with a slope. As an example, the slope can beabout 60 degrees.

FIGS. 18A-18C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first passivation layer 1810 overlying the first electrode1710 and the piezoelectric film 1620. In an example, the firstpassivation layer 1810 can include silicon nitride (SiN), silicon oxide(SiO), or other like materials. In a specific example, the firstpassivation layer 1810 can have a thickness ranging from about 50 nm toabout 100 nm.

FIGS. 19A-19C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a sacrificial layer 1910 overlying a portion of the firstelectrode 1810 and a portion of the piezoelectric film 1620. In anexample, the sacrificial layer 1910 can include polycrystalline silicon(poly-Si), amorphous silicon (a-Si), or other like materials. In aspecific example, this sacrificial layer 1910 can be subjected to a dryetch with a slope and be deposited with a thickness of about 1 um.Further, phosphorous doped SiO₂ (PSG) can be used as the sacrificiallayer with different combinations of support layer (e.g., SiNx).

FIGS. 20A-20C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a support layer 2010 overlying the sacrificial layer 1910, thefirst electrode 1710, and the piezoelectric film 1620. In an example,the support layer 2010 can include silicon dioxide (SiO₂), siliconnitride (SiN), or other like materials. In a specific example, thissupport layer 2010 can be deposited with a thickness of about 2-3 um. Asdescribed above, other support layers (e.g., SiNx) can be used in thecase of a PSG sacrificial layer.

FIGS. 21A-21C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofpolishing the support layer 2010 to form a polished support layer 2011.In an example, the polishing process can include a chemical-mechanicalplanarization process or the like.

FIGS. 22A-22C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate flipping thedevice and physically coupling overlying the support layer 2011overlying a bond substrate 2210. In an example, the bond substrate 2210can include a bonding support layer 2220 (SiO₂ or like material)overlying a substrate having silicon (Si), sapphire (Al₂O₃), silicondioxide (SiO₂), silicon carbide (SiC), or other like materials. In aspecific embodiment, the bonding support layer 2220 of the bondsubstrate 2210 is physically coupled to the polished support layer 2011.Further, the physical coupling process can include a room temperaturebonding process following by a 300 degree Celsius annealing process.

FIGS. 23A-23C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the growth substrate 1610 or otherwise the transfer of thepiezoelectric film 1620. In an example, the removal process can includea grinding process, a blanket etching process, a film transfer process,an ion implantation transfer process, a laser crack transfer process, orthe like and combinations thereof.

FIGS. 24A-24C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming an electrode contact via 2410 within the piezoelectric film 1620(becoming piezoelectric film 1621) overlying the first electrode 1710and forming one or more release holes 2420 within the piezoelectric film1620 and the first passivation layer 1810 overlying the sacrificiallayer 1910. The via forming processes can include various types ofetching processes.

FIGS. 25A-25C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second electrode 2510 overlying the piezoelectric film 1621.In an example, the formation of the second electrode 2510 includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching the second electrode 2510 to form anelectrode cavity 2511 and to remove portion 2511 from the secondelectrode to form a top metal 2520. Further, the top metal 2520 isphysically coupled to the first electrode 1720 through electrode contactvia 2410.

FIGS. 26A-26C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first contact metal 2610 overlying a portion of the secondelectrode 2510 and a portion of the piezoelectric film 1621, and forminga second contact metal 2611 overlying a portion of the top metal 2520and a portion of the piezoelectric film 1621. In an example, the firstand second contact metals can include gold (Au), aluminum (Al), copper(Cu), nickel (Ni), aluminum bronze (AlCu), or related alloys of thesematerials or other like materials.

FIGS. 27A-27C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second passivation layer 2710 overlying the second electrode2510, the top metal 2520, and the piezoelectric film 1621. In anexample, the second passivation layer 2710 can include silicon nitride(SiN), silicon oxide (SiOx), or other like materials. In a specificexample, the second passivation layer 2710 can have a thickness rangingfrom about 50 nm to about 100 nm.

FIGS. 28A-28C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the sacrificial layer 1910 to form an air cavity 2810. In anexample, the removal process can include a poly-Si etch or an a-Si etch,or the like.

FIGS. 29A-29C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the second electrode 2510 and the top metal 2520 toform a processed second electrode 2910 and a processed top metal 2920.This step can follow the formation of second electrode 2510 and topmetal 2520. In an example, the processing of these two componentsincludes depositing molybdenum (Mo), ruthenium (Ru), tungsten (W), orother like materials; and then etching (e.g., dry etch or the like) thismaterial to form the processed second electrode 2910 with an electrodecavity 2912 and the processed top metal 2920. The processed top metal2920 remains separated from the processed second electrode 2910 by theremoval of portion 2911. In a specific example, the processed secondelectrode 2910 is characterized by the addition of an energy confinementstructure configured on the processed second electrode 2910 to increaseQ.

FIGS. 30A-30C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 1710 to form a processed firstelectrode 2310. This step can follow the formation of first electrode1710. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 3010 with an electrode cavity,similar to the processed second electrode 2910. Air cavity 2811 showsthe change in cavity shape due to the processed first electrode 3010. Ina specific example, the processed first electrode 3010 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 3010 to increase Q.

FIGS. 31A-31C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 1710, to form a processed firstelectrode 2310, and the second electrode 2510/top metal 2520 to form aprocessed second electrode 2910/processed top metal 2920. These stepscan follow the formation of each respective electrode, as described forFIGS. 29A-29C and 30A-30C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

FIGS. 32A-32C through FIGS. 46A-46C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure withoutsacrificial layer. In these figure series described below, the “A”figures show simplified diagrams illustrating top cross-sectional viewsof single crystal resonator devices according to various embodiments ofthe present invention. The “B” figures show simplified diagramsillustrating lengthwise cross-sectional views of the same devices in the“A” figures. Similarly, the “C” figures show simplified diagramsillustrating widthwise cross-sectional views of the same devices in the“A” figures. In some cases, certain features are omitted to highlightother features and the relationships between such features. Those ofordinary skill in the art will recognize variations, modifications, andalternatives to the examples shown in these figure series.

FIGS. 32A-32C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming apiezoelectric film 3220 overlying a growth substrate 3210. In anexample, the growth substrate 3210 can include silicon (S), siliconcarbide (SiC), or other like materials. The piezoelectric film 3220 canbe an epitaxial film including aluminum nitride (AlN), gallium nitride(GaN), or other like materials. Additionally, this piezoelectricsubstrate can be subjected to a thickness trim.

FIGS. 33A-33C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstelectrode 3310 overlying the surface region of the piezoelectric film3220. In an example, the first electrode 3310 can include molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials. In aspecific example, the first electrode 3310 can be subjected to a dryetch with a slope. As an example, the slope can be about 60 degrees.

FIGS. 34A-34C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstpassivation layer 3410 overlying the first electrode 3310 and thepiezoelectric film 3220. In an example, the first passivation layer 3410can include silicon nitride (SiN), silicon oxide (SiOx), or other likematerials. In a specific example, the first passivation layer 3410 canhave a thickness ranging from about 50 nm to about 100 nm.

FIGS. 35A-35C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a supportlayer 3510 overlying the first electrode 3310, and the piezoelectricfilm 3220. In an example, the support layer 3510 can include silicondioxide (SiO₂), silicon nitride (SiN), or other like materials. In aspecific example, this support layer 3510 can be deposited with athickness of about 2-3 um. As described above, other support layers(e.g., SiNx) can be used in the case of a PSG sacrificial layer.

FIGS. 36A-36C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the optional method step of processingthe support layer 3510 (to form support layer 3511) in region 3610. Inan example, the processing can include a partial etch of the supportlayer 3510 to create a flat bond surface. In a specific example, theprocessing can include a cavity region. In other examples, this step canbe replaced with a polishing process such as a chemical-mechanicalplanarization process or the like.

FIGS. 37A-37C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming an air cavity3710 within a portion of the support layer 3511 (to form support layer3512). In an example, the cavity formation can include an etchingprocess that stops at the first passivation layer 3410.

FIGS. 38A-38C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming one or morecavity vent holes 3810 within a portion of the piezoelectric film 3220through the first passivation layer 3410. In an example, the cavity ventholes 3810 connect to the air cavity 3710.

FIGS. 39A-39C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate flipping the device and physicallycoupling overlying the support layer 3512 overlying a bond substrate3910. In an example, the bond substrate 3910 can include a bondingsupport layer 3920 (SiO₂ or like material) overlying a substrate havingsilicon (Si), sapphire (Al₂O₃), silicon dioxide (SiO₂), silicon carbide(SiC), or other like materials. In a specific embodiment, the bondingsupport layer 3920 of the bond substrate 3910 is physically coupled tothe polished support layer 3512. Further, the physical coupling processcan include a room temperature bonding process following by a 300 degreeCelsius annealing process.

FIGS. 40A-40C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of removing the growthsubstrate 3210 or otherwise the transfer of the piezoelectric film 3220.In an example, the removal process can include a grinding process, ablanket etching process, a film transfer process, an ion implantationtransfer process, a laser crack transfer process, or the like andcombinations thereof.

FIGS. 41A-41C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming an electrodecontact via 4110 within the piezoelectric film 3220 overlying the firstelectrode 3310. The via forming processes can include various types ofetching processes.

FIGS. 42A-42C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a secondelectrode 4210 overlying the piezoelectric film 3220. In an example, theformation of the second electrode 4210 includes depositing molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials; and thenetching the second electrode 4210 to form an electrode cavity 4211 andto remove portion 4211 from the second electrode to form a top metal4220. Further, the top metal 4220 is physically coupled to the firstelectrode 3310 through electrode contact via 4110.

FIGS. 43A-43C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to an example of the present invention. Asshown, these figures illustrate the method step of forming a firstcontact metal 4310 overlying a portion of the second electrode 4210 anda portion of the piezoelectric film 3220, and forming a second contactmetal 4311 overlying a portion of the top metal 4220 and a portion ofthe piezoelectric film 3220. In an example, the first and second contactmetals can include gold (Au), aluminum (Al), copper (Cu), nickel (Ni),aluminum bronze (AlCu), or other like materials. This figure also showsthe method step of forming a second passivation layer 4320 overlying thesecond electrode 4210, the top metal 4220, and the piezoelectric film3220. In an example, the second passivation layer 4320 can includesilicon nitride (SiN), silicon oxide (SiOx), or other like materials. Ina specific example, the second passivation layer 4320 can have athickness ranging from about 50 nm to about 100 nm.

FIGS. 44A-44C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process for single crystal acousticresonator devices according to another example of the present invention.As shown, these figures illustrate the method step of processing thesecond electrode 4210 and the top metal 4220 to form a processed secondelectrode 4410 and a processed top metal 4420. This step can follow theformation of second electrode 4210 and top metal 4220. In an example,the processing of these two components includes depositing molybdenum(Mo), ruthenium (Ru), tungsten (W), or other like materials; and thenetching (e.g., dry etch or the like) this material to form the processedsecond electrode 4410 with an electrode cavity 4412 and the processedtop metal 4420. The processed top metal 4420 remains separated from theprocessed second electrode 4410 by the removal of portion 4411. In aspecific example, the processed second electrode 4410 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 4410 to increase Q.

FIGS. 45A-45C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 3310 to form a processed firstelectrode 4510. This step can follow the formation of first electrode3310. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 4510 with an electrode cavity,similar to the processed second electrode 4410. Air cavity 3711 showsthe change in cavity shape due to the processed first electrode 4510. Ina specific example, the processed first electrode 4510 is characterizedby the addition of an energy confinement structure configured on theprocessed second electrode 4510 to increase Q.

FIGS. 46A-46C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process using a sacrificial layer forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 3310, to form a processed firstelectrode 4510, and the second electrode 4210/top metal 4220 to form aprocessed second electrode 4410/processed top metal 4420. These stepscan follow the formation of each respective electrode, as described forFIGS. 44A-44C and 45A-45C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

FIGS. 47A-47C through FIGS. 59A-59C illustrate a method of fabricationfor an acoustic resonator device using a transfer structure with amultilayer mirror structure. In these figure series described below, the“A” figures show simplified diagrams illustrating top cross-sectionalviews of single crystal resonator devices according to variousembodiments of the present invention. The “B” figures show simplifieddiagrams illustrating lengthwise cross-sectional views of the samedevices in the “A” figures. Similarly, the “C” figures show simplifieddiagrams illustrating widthwise cross-sectional views of the samedevices in the “A” figures. In some cases, certain features are omittedto highlight other features and the relationships between such features.Those of ordinary skill in the art will recognize variations,modifications, and alternatives to the examples shown in these figureseries.

FIGS. 47A-47C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a piezoelectric film 4720 overlying a growth substrate 4710. Inan example, the growth substrate 4710 can include silicon (S), siliconcarbide (SiC), or other like materials. The piezoelectric film 4720 canbe an epitaxial film including aluminum nitride (AlN), gallium nitride(GaN), or other like materials. Additionally, this piezoelectricsubstrate can be subjected to a thickness trim.

FIGS. 48A-48C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first electrode 4810 overlying the surface region of thepiezoelectric film 4720. In an example, the first electrode 4810 caninclude molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials. In a specific example, the first electrode 4810 can besubjected to a dry etch with a slope. As an example, the slope can beabout 60 degrees.

FIGS. 49A-49C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a multilayer mirror or reflector structure. In an example, themultilayer mirror includes at least one pair of layers with a lowimpedance layer 4910 and a high impedance layer 4920. In FIGS. 49A-49C,two pairs of low/high impedance layers are shown (low: 4910 and 4911;high: 4920 and 4921). In an example, the mirror/reflector area can belarger than the resonator area and can encompass the resonator area. Ina specific embodiment, each layer thickness is about ¼ of the wavelengthof an acoustic wave at a targeting frequency. The layers can bedeposited in sequence and be etched afterwards, or each layer can bedeposited and etched individually. In another example, the firstelectrode 4810 can be patterned after the mirror structure is patterned.

FIGS. 50A-50C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a support layer 5010 overlying the mirror structure (layers4910, 4911, 4920, and 4921), the first electrode 4810, and thepiezoelectric film 4720. In an example, the support layer 5010 caninclude silicon dioxide (SiO₂), silicon nitride (SiN), or other likematerials. In a specific example, this support layer 5010 can bedeposited with a thickness of about 2-3 um. As described above, othersupport layers (e.g., SiNx) can be used.

FIGS. 51A-51C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofpolishing the support layer 5010 to form a polished support layer 5011.In an example, the polishing process can include a chemical-mechanicalplanarization process or the like.

FIGS. 52A-52C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate flipping thedevice and physically coupling overlying the support layer 5011overlying a bond substrate 5210. In an example, the bond substrate 5210can include a bonding support layer 5220 (SiO₂ or like material)overlying a substrate having silicon (Si), sapphire (Al₂O₃), silicondioxide (SiO₂), silicon carbide (SiC), or other like materials. In aspecific embodiment, the bonding support layer 5220 of the bondsubstrate 5210 is physically coupled to the polished support layer 5011.Further, the physical coupling process can include a room temperaturebonding process following by a 300 degree Celsius annealing process.

FIGS. 53A-53C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step ofremoving the growth substrate 4710 or otherwise the transfer of thepiezoelectric film 4720. In an example, the removal process can includea grinding process, a blanket etching process, a film transfer process,an ion implantation transfer process, a laser crack transfer process, orthe like and combinations thereof.

FIGS. 54A-54C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming an electrode contact via 5410 within the piezoelectric film 4720overlying the first electrode 4810. The via forming processes caninclude various types of etching processes.

FIGS. 55A-55C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a second electrode 5510 overlying the piezoelectric film 4720.In an example, the formation of the second electrode 5510 includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching the second electrode 5510 to form anelectrode cavity 5511 and to remove portion 5511 from the secondelectrode to form a top metal 5520. Further, the top metal 5520 isphysically coupled to the first electrode 5520 through electrode contactvia 5410.

FIGS. 56A-56C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to an example of thepresent invention. As shown, these figures illustrate the method step offorming a first contact metal 5610 overlying a portion of the secondelectrode 5510 and a portion of the piezoelectric film 4720, and forminga second contact metal 5611 overlying a portion of the top metal 5520and a portion of the piezoelectric film 4720. In an example, the firstand second contact metals can include gold (Au), aluminum (Al), copper(Cu), nickel (Ni), aluminum bronze (AlCu), or other like materials. Thisfigure also shows the method step of forming a second passivation layer5620 overlying the second electrode 5510, the top metal 5520, and thepiezoelectric film 4720. In an example, the second passivation layer5620 can include silicon nitride (SiN), silicon oxide (SiOx), or otherlike materials. In a specific example, the second passivation layer 5620can have a thickness ranging from about 50 nm to about 100 nm.

FIGS. 57A-57C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the second electrode 5510 and the top metal 5520 toform a processed second electrode 5710 and a processed top metal 5720.This step can follow the formation of second electrode 5710 and topmetal 5720. In an example, the processing of these two componentsincludes depositing molybdenum (Mo), ruthenium (Ru), tungsten (W), orother like materials; and then etching (e.g., dry etch or the like) thismaterial to form the processed second electrode 5410 with an electrodecavity 5712 and the processed top metal 5720. The processed top metal5720 remains separated from the processed second electrode 5710 by theremoval of portion 5711. In a specific example, this processing givesthe second electrode and the top metal greater thickness while creatingthe electrode cavity 5712. In a specific example, the processed secondelectrode 5710 is characterized by the addition of an energy confinementstructure configured on the processed second electrode 5710 to increaseQ.

FIGS. 58A-58C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 4810 to form a processed firstelectrode 5810. This step can follow the formation of first electrode4810. In an example, the processing of these two components includesdepositing molybdenum (Mo), ruthenium (Ru), tungsten (W), or other likematerials; and then etching (e.g., dry etch or the like) this materialto form the processed first electrode 5810 with an electrode cavity,similar to the processed second electrode 5710. Compared to the twoprevious examples, there is no air cavity. In a specific example, theprocessed first electrode 5810 is characterized by the addition of anenergy confinement structure configured on the processed secondelectrode 5810 to increase Q.

FIGS. 59A-59C are simplified diagrams illustrating variouscross-sectional views of a single crystal acoustic resonator device andof method steps for a transfer process with a multilayer mirror forsingle crystal acoustic resonator devices according to another exampleof the present invention. As shown, these figures illustrate the methodstep of processing the first electrode 4810, to form a processed firstelectrode 5810, and the second electrode 5510/top metal 5520 to form aprocessed second electrode 5710/processed top metal 5720. These stepscan follow the formation of each respective electrode, as described forFIGS. 57A-57C and 58A-58C. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

In each of the preceding examples relating to transfer processes, energyconfinement structures can be formed on the first electrode, secondelectrode, or both. In an example, these energy confinement structuresare mass loaded areas surrounding the resonator area. The resonator areais the area where the first electrode, the piezoelectric layer, and thesecond electrode overlap. The larger mass load in the energy confinementstructures lowers a cut-off frequency of the resonator. The cut-offfrequency is the lower or upper limit of the frequency at which theacoustic wave can propagate in a direction parallel to the surface ofthe piezoelectric film. Therefore, the cut-off frequency is theresonance frequency in which the wave is travelling along the thicknessdirection and thus is determined by the total stack structure of theresonator along the vertical direction. In piezoelectric films (e.g.,AlN), acoustic waves with lower frequency than the cut-off frequency canpropagate in a parallel direction along the surface of the film, i.e.,the acoustic wave exhibits a high-band-cut-off type dispersioncharacteristic. In this case, the mass loaded area surrounding theresonator provides a barrier preventing the acoustic wave frompropagating outside the resonator. By doing so, this feature increasesthe quality factor of the resonator and improves the performance of theresonator and, consequently, the filter.

In addition, the top single crystalline piezoelectric layer can bereplaced by a polycrystalline piezoelectric film. In such films, thelower part that is close to the interface with the substrate has poorcrystalline quality with smaller grain sizes and a wider distribution ofthe piezoelectric polarization orientation than the upper part of thefilm close to the surface. This is due to the polycrystalline growth ofthe piezoelectric film, i.e., the nucleation and initial film haverandom crystalline orientations. Considering AlN as a piezoelectricmaterial, the growth rate along the c-axis or the polarizationorientation is higher than other crystalline orientations that increasethe proportion of the grains with the c-axis perpendicular to the growthsurface as the film grows thicker. In a typical polycrystalline AlN filmwith about a 1 um thickness, the upper part of the film close to thesurface has better crystalline quality and better alignment in terms ofpiezoelectric polarization. By using the thin film transfer processcontemplated in the present invention, it is possible to use the upperportion of the polycrystalline film in high frequency BAW resonatorswith very thin piezoelectric films. This can be done by removing aportion of the piezoelectric layer during the growth substrate removalprocess. Of course, there can be other variations, modifications, andalternatives.

In an example, the present invention provides a high-performance,ultra-small pass-band Bulk Acoustic Wave (BAW) Radio Frequency (RF)Filter for use in 4.5G applications. This circuit device has a passbandwithin the LTE over Citizen Broadband Radio Service (CBRS) B48 and B49bands and a stopband rejecting signals below 3.55 GHz and above 3.7 GHz.Further details of these CBRS bands are shown in FIG. 60 .

FIG. 60 is a simplified diagram illustrating filter pass-bandrequirements in a radio frequency spectrum according to an example ofthe present invention. As shown, the frequency spectrum 6000 shows arange from about 3.0 GHz to about 6.0 GHz. Here, a first applicationband (3.3 GHz-4.2 GHz) 6010 is configured for 5G n77 applications. Thisband includes a 5G sub-band (3.3 GHz-3.8 GHz) 6011, which includesfurther LTE sub-bands (3.4 GHz-3.6 GHz) 6012, B43 (3.6 GHz-3.8 GHz)6013, and CBRS (3.55 GHz-3.7 GHz) 6014. The CBRS band 6014 covers theCBRS LTE B48 and B49 bands. A second application band (4.4 GHz-5.0 GHz)6020 is configured for 5G n79 applications and also includes a sub-band6021 for China specific applications. Those of ordinary skill in the artwill recognize other variations, modifications, and alternatives.

A third application band 6030, labeled (5.15 GHz-5.925), can beconfigured for the 5.5 GHz Wi-Fi and 5G applications. In an example,this band can include a B252 sub-band (5.15 GHz-5.25 GHz) 6031, a B255sub-band (5.735 GHz-5850 GHz) 6032, and a B47 sub-band (5.855 GHz-5.925GHz) 6033. These sub-bands can be configured alongside a UNII-1 band(5.15 GHz-5.25 GHz) 6034, a UNII-2A band (5.25 GHz-5.33 GHz) 6035, aUNII-2C band (5.49 GHz-5.735 GHz) 6036, a UNII-3 band (5.725 GHz-5.835GHz) 6037, and a UNII-4 band (5.85 GHz-5.925 GHz) 6038. These bands cancoexist with additional bands configured following the third applicationband 6030 for other applications. Of course, there can be othervariations, modifications, and alternatives.

In an embodiment, the present filter utilizes high purity piezoelectricXBAW technology as described in the previous figures. This filterprovides low insertion loss and meets the stringent rejectionrequirements in the 5G and LTE licensed and CBRS shared spectrum. Thehigh-power rating satisfies the demanding power requirements of thelatest standards.

FIG. 61 is a simplified diagram illustrating an overview of key marketsthat are applications for acoustic wave RF filters according to anexample of the present invention. The application chart 6100 for3.55-3.7 GHz BAW RF filters shows mobile devices, smartphones,automobiles, Wi-Fi tri-band routers, tri-band mobile devices, tri-bandsmartphones, integrated cable modems, Wi-Fi tri-band access points,LTE-U/LAA small cells, and the like. A schematic representation of thefrequency spectrum used in a 5G system is provided in FIG. 62 .

FIG. 62 is a simplified diagram illustrating application areas for3.55-3.7 GHz RF filters in mobile applications according to examples ofthe present invention. As shown in diagram 6200, RF filters used bycommunication devices can be configured for specific applications at aspecific band of operation. In a specific example, a mobile applicationarea can be designated at the frequency range between 3550 MHz and 3700MHz, which the 3.55-3.7 GHz RF filter can configure as the pass-band.The other frequency ranges (600 MHz to 1000 MHz, 1785 MHz to 2690 MHz,4400 MHz to 5000 MHz, and 5150 MHz to 5850 MHz) are rejected. Those ofordinary skill in the art will recognize other variations,modifications, and alternatives.

The present invention includes resonator and RF filter devices usingboth textured polycrystalline materials (deposited using PVD methods)and single crystal piezoelectric materials (grown using CVD techniqueupon a seed substrate). Various substrates can be used for fabricatingthe acoustic devices, such silicon substrates of variouscrystallographic orientations and the like. Additionally, the presentmethod can use sapphire substrates, silicon carbide substrates, galliumnitride (GaN) bulk substrates, or aluminum nitride (AlN) bulksubstrates. The present method can also use GaN templates, AlNtemplates, and AlxGa1-xN templates (where x varies between 0.0 and 1.0).These substrates and templates can have polar, non-polar, or semi-polarcrystallographic orientations. Further the piezoelectric materialsdeposed on the substrate can include allows selected from at least oneof the following: AlN, MgHfAlN, GaN, InN, InGaN, AlInN, AlInGaN, ScAlN,ScAlGaN, ScGaN, ScN, BAlN, BAlScN, and BN.

The resonator and filter devices may employ process technologiesincluding but not limited to Solidly-Mounted Resonator (SMR), Film BulkAcoustic Resonator (FBAR), or XBAW technology. Representativecross-sections are shown below in FIGS. 63A-63C. For clarification, theterms “top” and “bottom” used in the present specification are notgenerally terms in reference of a direction of gravity. Rather, theterms “top” and “bottom” are used in reference to each other in thecontext of the present device and related circuits. Those of ordinaryskill in the art will recognize other variations, modifications, andalternatives.

In an example, the piezoelectric layer ranges between 0.1 and 2.0 um andis optimized to produced optimal combination of resistive and acousticlosses. The thickness of the top and bottom electrodes range can between250 #Å and 2500 Å and the metal consists of a refractory metal with highacoustic velocity and low resistivity. In a specific example, theresonators can be “passivated” with a dielectric (not shown in FIGS.63A-63C) consisting of a nitride and or an oxide and whose range isbetween 100 Å and 2000 Å. In this case, the dielectric layer is used toadjust resonator resonance frequency. Extra care is taken to reduce themetal resistivity between adjacent resonators on a metal layer calledthe interconnect metal. The thickness of the interconnect metal canrange between 500 Å and 5 um. The resonators contain at least one aircavity interface in the case of SMRs and two air cavity interfaces inthe case of FBARs and XBAWs. In an example, the shape of the resonatorscan be selected from asymmetrical shapes including ellipses, rectangles,and polygons, and the like. Further, the resonators contain reflectingfeatures near the resonator edge on one or both sides of the resonator.

FIGS. 63A-63C are simplified diagrams illustrating cross-sectional viewsof resonator devices according to various examples of the presentinvention. More particularly, device 6301 of FIG. 63A shows a BAWresonator device including an SMR, FIG. 63B shows a BAW resonator deviceincluding an FBAR, and FIG. 63C shows a BAW resonator device with asingle crystal XBAW. As shown in SMR device 6301, a reflector device6320 is configured overlying a substrate member 6310. The reflectordevice 6320 can be a Bragg reflector or the like. A bottom electrode6330 is configured overlying the reflector device 6320. Apolycrystalline piezoelectric layer 6340 is configured overlying thebottom electrode 6330. Further, a top electrode 6350 is configuredoverlying the polycrystalline layer 6340. As shown in the FBAR device6302, the layered structure including the bottom electrode 6330, thepolycrystalline layer 6340, and the top electrode 6350 remains the same.The substrate member 6311 includes an air cavity 6312, and a dielectriclayer is formed overlying the substrate member 6311 and covering the aircavity 6312. As shown in XBAW device 6303, the substrate member 6311also contains an air cavity 6312, but the bottom electrode 6330 isformed within a region of the air cavity 6312. A single crystalpiezoelectric layer is formed overlying the substrate member 6311, theair cavity 6312, and the bottom electrode 6341. Further, a top electrode6350 is formed overlying a portion of the single crystal layer 6341.These resonators can be scaled and configured into circuitconfigurations shown in FIGS. 64A-64C.

The RF filter circuit can comprise various circuit topologies, includingmodified lattice (“I”) 6401, lattice (“II”) 6402, and ladder (“III”)6403 circuit configurations, as shown in FIGS. 64A, 64B, and 64C,respectively. These figures are representative lattice and ladderdiagrams for acoustic filter designs including resonators and otherpassive components. The lattice and modified lattice configurationsinclude differential input ports 6410 and differential output ports6450, while the ladder configuration includes a single-ended input port6411 and a single-ended output port 6450. In the lattice configurations,nodes are denoted by top nodes (t1-t3) and bottom nodes (b1-b3), whilein the ladder configuration the nodes are denoted as one set of nodes(n1-n4). The series resonator elements (in cases I, II, and III) areshown with white center elements 6421-6424 and the shunt resonatorelements have darkened center circuit elements 6431-6434. The serieselements resonance frequency is higher than the shunt elements resonancefrequency in order to form the filter skirt at the pass-band frequency.The inductors 6441-6443 shown in the modified lattice circuit diagram(FIG. 64A) and any other matching elements can be included eitheron-chip (in proximity to the resonator elements) or off-chip (nearby tothe resonator chip) and can be used to adjust frequency pass-band and/ormatching of impedance (to achieve the return loss specification) for thefilter circuit. The filter circuit contains resonators with at least tworesonance frequencies. The center of the pass-band frequency can beadjusted by a trimming step (using an ion milling technique or otherlike technique) and the shape the filter skirt can be adjusted bytrimming individual resonator elements (to vary the resonance frequencyof one or more elements) in the circuit.

In an example, the present invention provides an RF filter circuitdevice using a ladder configuration including a plurality of resonatordevices and a plurality of shunt configuration resonator devices. Eachof the plurality of resonator devices includes at least a capacitordevice, a bottom electrode, a piezoelectric material, a top electrode,and an insulating material configured in accordance to any of theresonator examples described previously. The plurality of resonatordevices is configured in a serial configuration, while the plurality ofshunt configuration resonators is configured in a parallel configurationsuch that one of the plurality of shunt configuration resonators iscoupled to the serial configuration following each of the plurality ofresonator devices.

In an example, the RF filter circuit device in a ladder configurationcan also be described as follows. The device can include an input port,a first node coupled to the input port, a first resonator coupledbetween the first node and the input port. A second node is coupled tothe first node and a second resonator is coupled between the first nodeand the second node. A third node is coupled to the second node and athird resonator is coupled between the second node and the third node. Afourth node is coupled to the third node and a fourth resonator iscoupled between the third node and the output port. Further, an outputport is coupled to the fourth node. Those of ordinary skill in the artwill recognize other variations, modifications, and alternatives.

Each of the first, second, third, and fourth resonators can include acapacitor device. Each such capacitor device can include a substratemember, which has a cavity region and an upper surface region contiguouswith an opening in the first cavity region. Each capacitor device caninclude a bottom electrode within a portion of the cavity region and apiezoelectric material overlying the upper surface region and the bottomelectrode. Also, each capacitor device can include a top electrodeoverlying the piezoelectric material and the bottom electrode, as wellas an insulating material overlying the top electrode and configuredwith a thickness to tune the resonator.

The device also includes a serial configuration includes the input port,the first node, the first resonator, the second node, the secondresonator, the third node, the third resonator, the fourth resonator,the fourth node, and the output port. A separate shunt configurationresonator is coupled to each of the first, second, third, fourth nodes.A parallel configuration includes the first, second, third, and fourthshunt configuration resonators. Further, a circuit response can beconfigured between the input port and the output port and configuredfrom the serial configuration and the parallel configuration to achievea transmission loss from a pass-band having a characteristic frequencycentered around 3.625 GHz and having a bandwidth from 3.55 GHz to 3.7GHz such that the characteristic frequency centered around 3.625 GHz istuned from a lower frequency ranging from about 2.9 GHz to 3.5 GHz.

In an example, the piezoelectric materials can include single crystalmaterials, polycrystalline materials, or combinations thereof and thelike. The piezoelectric materials can also include a substantiallysingle crystal material that exhibits certain polycrystalline qualities,i.e., an essentially single crystal material. In a specific example, thefirst, second, third, and fourth piezoelectric materials are eachessentially a single crystal aluminum nitride (AlN) bearing material oraluminum scandium nitride (AlScN) bearing material, a single crystalgallium nitride (GaN) bearing material or gallium aluminum nitride(GaAlN) bearing material, a magnesium hafnium aluminum nitride (MgHfAlN)material, or the like. In other specific examples, these piezoelectricmaterials each comprise a polycrystalline aluminum nitride (AlN) bearingmaterial or aluminum scandium nitride (AlScN) bearing material, or apolycrystalline gallium nitride (GaN) bearing material or galliumaluminum nitride (GaAlN) bearing material, a magnesium hafnium aluminumnitride (MgHfAlN) material, or the like. In other examples, thepiezoelectric materials can include aluminum gallium nitride(Al_(x)Ga_(1-x)N) material or an aluminum scandium nitride(Al_(x)Sc_(1-x)N) material characterized by a composition of 0≤X<1.0. Asdiscussed previously, the thicknesses of the piezoelectric materials canvary, and in some cases can be greater than 250 nm.

In a specific example, the piezoelectric material can be configured as alayer characterized by an x-ray diffraction (XRD) rocking curve fullwidth at half maximum ranging from 0 degrees to 2 degrees. The x-rayrocking curve FWHM parameter can depend on the combination of materialsused for the piezoelectric layer and the substrate, as well as thethickness of these materials. Further, an FWHM profile is used tocharacterize material properties and surface integrity features, and isan indicator of crystal quality/purity. The acoustic resonator devicesusing single crystal materials exhibit a lower FWHM compared to devicesusing polycrystalline material, i.e., single crystal materials have ahigher crystal quality or crystal purity.

In a specific example, the serial configuration forms a resonanceprofile and an anti-resonance profile. The parallel configuration alsoforms a resonance profile and an anti-resonance profile. These profilesare such that the resonance profile from the serial configuration isoff-set with the anti-resonance profile of the parallel configuration toform the pass-band.

In a specific example, the pass-band is characterized by a band edge oneach side of the pass-band and having an amplitude difference rangingfrom 10 dB to 60 dB. The pass-band has a pair of band edges; each ofwhich has a transition region from the pass-band to a stop band suchthat the transition region is no greater than 250 MHz. In anotherexample, pass-band can include a pair of band edges and each of theseband edges can have a transition region from the pass-band to a stopband such that the transition region ranges from 5 MHz to 250 MHz.

In a specific example, each of the first, second, third, and fourthinsulating materials comprises a silicon nitride bearing material or anoxide bearing material configured with a silicon nitride material anoxide bearing material.

In a specific example, the present device can further include severalfeatures. The device can further include a rejection band rejectingsignals below 3.55 GHz and above 3.7 GHz. The device can further includean insertion loss of less than 2.5 dB and a maximum amplitude variationcharacterizing the pass-band of less than 1.5 dB. Also, the device caninclude a minimum attenuation of 40 dB for a frequency range of 700 MHzto 1000 MHz; a minimum attenuation of 45 dB for a frequency range of1900 MHz to 2400 MHz; a minimum attenuation of 50 dB for a frequencyrange of 2400 MHz to 2500 MHz; a minimum attenuation of 45 dB for afrequency range of 2500 MHz to 3340 MHz; a minimum attenuation of 40 dBfor a frequency range of 3340 MHz to 3450 MHz; a minimum attenuation of12 dB for a frequency range of 3450 MHz to 3530 MHz; a minimumattenuation of 12 dB for a frequency range of 3720 MHz to 3800 MHz; aminimum attenuation of 30 dB for a frequency range of 3800 MHz to 3910MHz; a minimum attenuation of 40 dB for a frequency range of 3910 MHz to4200 MHz; and a minimum attenuation of 50 dB for a frequency range of5100 MHz to 5900 MHz. The device can further include a minimum returnloss characterizing the pass-band of 10 dB and the device can beoperable from −40 Degrees Celsius to 85 Degrees Celsius. The device canfurther include a maximum power handling capability within the pass-bandof at least +27 dBm or 0.5 Watt. Further, the pass-band can beconfigured for 4.5G CBRS LTE applications.

In a specific example, the present device can be configured as a bulkacoustic wave (BAW) filter device. Each of the first, second, third, andfourth resonators can be a BAW resonator. Similarly, each of the first,second, third, and fourth shunt resonators can be BAW resonators. Thepresent device can further include one or more additional resonatordevices numbered from N to M, where N is four and M is twenty.Similarly, the present device can further include one or more additionalshunt resonator devices numbered from N to M, where N is four and M istwenty. In other examples, the present device can include a plurality ofresonator devices configured with a plurality of shunt resonator devicesin a ladder configuration, a lattice configuration, or otherconfiguration as previously described.

In an example, the present invention provides an RF filter circuitdevice using a lattice configuration including a plurality of topresonator devices, a plurality of bottom resonator devices, and aplurality of shunt configuration resonator devices. Similar to theladder configuration RF filter circuit, each of the plurality of top andbottom resonator devices includes at least a capacitor device, a bottomelectrode, a piezoelectric material, a top electrode, and an insulatingmaterial configured in accordance to any of the resonator examplesdescribed previously. The plurality of top resonator devices isconfigured in a top serial configuration and the plurality of bottomresonator devices is configured in a bottom serial configuration.Further, the plurality of shunt configuration resonators is configuredin a cross-coupled configuration such that a pair of the plurality ofshunt configuration resonators is cross-coupled between the top serialconfiguration and the bottom serial configuration and between one of theplurality of top resonator devices and one of the plurality of thebottom resonator devices. In a specific example, this device alsoincludes a plurality of inductor devices, wherein the plurality ofinductor devices are configured such that one of the plurality ofinductor devices is coupled between the differential input port, one ofthe plurality of inductor devices is coupled between the differentialoutput port, and one of the plurality of inductor devices is coupled tothe top serial configuration and the bottom serial configuration betweeneach cross-coupled pair of the plurality of shunt configurationresonators.

In an example, the RF circuit device in a lattice configuration can alsobe described as follows. The device can include a differential inputport, a top serial configuration, a bottom serial configuration, a firstlattice configuration, a second lattice configuration, and adifferential output port. The top serial configuration can include afirst top node, a second top node, and a third top node. A first topresonator can be coupled between the first top node and the second topnode, while a second top resonator can be coupled between the second topnode and the third top node. Similarly, the bottom serial configurationcan include a first bottom node, a second bottom node, and a thirdbottom node. A first bottom resonator can be coupled between the firstbottom node and the second bottom node, while a second bottom resonatorcan be coupled between the second bottom node and the third bottom node.

In an example, the first lattice configuration includes a first shuntresonator cross-coupled with a second shunt resonator and coupledbetween the first top resonator of the top serial configuration and thefirst bottom resonator of the bottom serial configuration. Similarly,the second lattice configuration can include a first shunt resonatorcross-coupled with a second shunt resonator and coupled between thesecond top resonator of the top serial configuration and the secondbottom resonator of the bottom serial configuration. The top serialconfiguration and the bottom serial configuration can each be coupled toboth the differential input port and the differential output port.

In a specific example, the device further includes a first balun coupledto the differential input port and a second balun coupled to thedifferential output port. The device can further include an inductordevice coupled between the differential input and output ports. In aspecific example, the device can further include a first inductor devicecoupled between the first top node of the top serial configuration andthe first bottom node of the bottom serial configuration; a secondinductor device coupled between the second top node of the top serialconfiguration and the second bottom node of the bottom serialconfiguration; and a third inductor device coupled between the third topnode of the top serial configuration and the third bottom node of thebottom serial configuration.

The packaging approach includes but is not limited to wafer levelpackaging (WLP), WLP-plus-cap wafer approach, flip-chip, chip and bondwire, as shown in FIGS. 65 and 66 . One or more RF filter chips and oneor more filter bands can be packaged within the same housingconfiguration. Each RF filter band within the package can include one ormore resonator filter chips and passive elements (capacitors, inductors)can be used to tailor the bandwidth and frequency spectrumcharacteristic. For a 5G system application, a package configurationsupporting four RF filter bands, including the n77, n78, n79, and n41GHz bandpass solutions is capable of being addressed with the BAW RFfilter technology.

FIG. 65A is a simplified diagram illustrating a packing approachaccording to an example of the present invention. As shown, device 6501is packaged using a conventional die bond of an RF filter die 6510 tothe base 6520 of a package and metal bond wires 6530 to the RF filterchip from the circuit interface 6540.

FIG. 65B is as simplified diagram illustrating a packing approachaccording to an example of the present invention. As shown, device 6502is packaged using a flip-mount wafer level package (WLP) showing the RFfilter silicon die 6510 mounted to the circuit interface 6540 usingcopper pillars 6531 or other high-conductivity interconnects.

FIGS. 66A-66B are simplified diagrams illustrating packing approachesaccording to examples of the present invention. In FIG. 66A, device 6601shows an alternate version of a WLP utilizing a BAW RF filter circuitMEMS device 6631 and a substrate 6611 to a cap wafer 6641. In anexample, the cap wafer 6641 may include thru-silicon-vias (TSVs) toelectrically connect the RF filter MEMS device 6631 to the topside ofthe cap wafer (not shown in the figure). The cap wafer 6641 can becoupled to a dielectric layer 6621 overlying the substrate 6611 andsealed by sealing material 6651.

In FIG. 66B, device 6602 shows another version of a WLP bonding aprocessed BAW substrate 6612 to a cap layer 6642. As discussedpreviously, the cap wafer 6642 may include thru-silicon vias (TSVs) 6632spatially configured through a dielectric layer 6622 to electricallyconnect the BAW resonator within the BAW substrate 6612 to the topsideof the cap wafer. Similar to the device of FIG. 66A, the cap wafer 6642can be coupled to a dielectric layer overlying the BAW substrate 6612and sealed by sealing material 6652. Of course, there can be othervariations, modifications, and alternatives.

In an example, the present filter passes frequencies in the range of3.55 to 3.7 GHz and rejects frequencies outside of this pass-band.Additional features of the acoustic wave filter circuit are providedbelow. The circuit symbol which is used to reference the RF filterbuilding block is provided in FIG. 67 . The electrical performancespecifications of the filter are provided in FIG. 68 and the passbandperformance of the filter is provided in FIG. 69 .

In an example, the present invention provides a high-performance,ultra-small pass-band Bulk Acoustic Wave (BAW) Radio Frequency (RF)Filter for use in 5.2 GHz Wi-Fi applications covering U-NII-1 plusU-NII-2A bands.

In various examples, the present filter can have certain features. Thedie configuration can be less than 2 mm×2 mm×0.5 mm; in a specificexample, the die configuration is typically less than 1 mm×1 mm×0.2 mm.The packaged device has an ultra-small form factor, such as a 1.1 mm×0.9mm×0.3 mm for a WLP approach, shown in FIGS. 65B, 66A, and 66B. A largerform factor, such as a 2 mm×2.5 mm×0.9 mm, is available using a wirebond approach, shown in FIG. 65A, for higher power applications. In aspecific example, the device is configured with a single-ended 50-Ohmantenna, and transmitter/receiver (Tx/Rx) ports. The high rejection ofthe device enables coexistence with adjacent Wi-Fi UNIT bands. Thedevice is also be characterized by a high power rating (maximum greaterthan +30 dBm), a low insertion loss pass-band filter with less than 1.5dB transmission loss, and performance over a temperature range from −40degrees Celsius to +85 degrees Celsius. Further, in a specific example,the device is RoHS (Restriction of Hazardous Substances) compliant anduses Pb-free (lead-free) packaging.

FIG. 67 is a simplified circuit diagram illustrating a 2-port BAW RFfilter circuit according to an example of the present invention. Asshown, circuit 6700 includes a first port (“Port 1”) 6711, a second port(“Port 2”) 6712, and a filter 6720. The first port represents aconnection from a transmitter (TX) or received (RX) to the filter 6720and the second port represents a filter connection from the filter 6720to an antenna (ANT).

FIG. 68 is a simplified table of filter parameters according to anexample of the present invention. As shown, table 6800 includeselectrical specifications for a 3.55-3.7 GHz RF resonator filtercircuit. The circuit parameters are provided along with thespecification units, minimum, along with typical and maximumspecification values.

FIG. 69A is a simplified graph representing insertion loss overfrequency according to an example of the present invention. As shown,graph 6901 represents a narrowband measured versus modeled response 6911for a 3.55-3.7 GHz RF filter using a ladder RF filter configuration. Themodeled curve is the transmission loss (s21) predicted from a linearsimulation tool incorporating non-linear, full 3-dimensional (3D)electromagnetic (EM) simulation.

FIG. 69B is a simplified graph representing insertion loss overfrequency according to an example of the present invention. As shown,graph 6902 represents a wideband measured versus modeled response 6913for a 3.55-3.7 GHz RF filter using a ladder RF filter configuration. Themodeled curve is the transmission loss (s21) predicted from a linearsimulation tool incorporating non-linear, full 3-dimensional (3D)electromagnetic (EM) simulation.

Referring back to FIG. 60 , which illustrates filter pass-bandrequirements in a radio frequency spectrum according to an example ofthe present invention, third application band 6030 includes a UNII-1band 6031 (5.15 GHz-5.25 GHz) and a UNII-2A band 6032 (5.25 GHz-5.33GHz). An LTE band 6033 overlaps the same frequency range as the UNII-1band 6031. Finally, a fourth application band 6040 includes a UNII-2Cband 6041 (5.490 GHz-5.735 GHz), a UNII-3 band 6042 (5.735 GHz-5.85GHz), and a UNII-4 band 6043 (5.85 GHz-5.925 GHz). An LTE band 6044shares the same frequency range as the UNII-2C band 6041, while asub-band 6045 overlaps the same frequency range as the UNII-4 band 6043and an LTE band 6046 overlaps a smaller subsection of the same frequencyrange (5.855 GHz-5.925 GHz). Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. Therefore, the above description and illustrations shouldnot be taken as limiting the scope of the present invention which isdefined by the appended claims.

In an embodiment, the present filter utilizes single crystal BAWtechnology as described in the previous figures. This filter provideslow insertion loss and meets the stringent rejection requirementsenabling coexistence with U-NII-2C and U-NII-3 bands. The high-powerrating satisfies the demanding power requirements of the latest Wi-Fistandards.

Referring back to FIG. 61 , which is a simplified diagram illustratingan overview of key markets that are applications for acoustic wave RFfilters according to an example of the present invention. Theapplication chart 6100 for 5.2 GHz BAW RF filters shows mobile devices,smartphones, automobiles, Wi-Fi tri-band routers, tri-band mobiledevices, tri-band smartphones, integrated cable modems, Wi-Fi tri-bandaccess points, LTE/LAA small cells, and the like. A schematicrepresentation of the frequency spectrum used in a tri-band Wi-Fi systemis provided in FIG. 70 .

FIG. 70 is a simplified diagram illustrating application areas for 5.2GHz RF filters in Tri-Band Wi-Fi radios according to examples of thepresent invention. As shown, RF filters used by communication devices6210 can be configured for specific applications at three separate bandsof operation. In a specific example, application area 6220 operates at2.4 GHz and includes computing and mobile devices, application area 6230operates at 5.2 GHz and includes television and display devices, andapplication area 6240 operates at 5.6 GHz and includes video gameconsole and handheld devices. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

The present invention includes resonator and RF filter devices usingboth textured polycrystalline piezoelectric materials (deposited usingPVD methods) and single crystal piezoelectric materials (grown using CVDtechnique upon a seed substrate). Various substrates can be used forfabricating the acoustic devices, such silicon substrates of variouscrystallographic orientations and the like. Additionally, the presentmethod can use sapphire substrates, silicon carbide substrates, galliumnitride (GaN) bulk substrates, or aluminum nitride (AlN) bulksubstrates. The present method can also use GaN templates, AlNtemplates, and AlxGa1-xN templates (where x varies between 0.0 and 1.0).These substrates and templates can have polar, non-polar, or semi-polarcrystallographic orientations. Further the piezoelectric materialsdeposed on the substrate can include allows selected from at least oneof the following: AlN, AlN, GaN, InN, InGaN, AlInN, AlInGaN, ScAlN,ScAlGaN, ScGaN, ScN, BAlN, BAlScN, and BN.

The resonator and filter devices may employ process technologiesincluding but not limited to Solidly-Mounted Resonator (SMR), Film BulkAcoustic Resonator (FBAR), or Single Crystal Bulk Acoustic Resonator(XBAW). Representative cross-sections are shown in FIGS. 63A-63C, whichare simplified diagrams illustrating cross-sectional views of resonatordevices according to various examples of the present invention. Forclarification, the terms “top” and “bottom” used in the presentspecification are not generally terms in reference of a direction ofgravity. Rather, the terms “top” and “bottom” are used in reference toeach other in the context of the present device and related circuits.Those of ordinary skill in the art will recognize other variations,modifications, and alternatives.

In an example, the piezoelectric layer ranges between 0.1 and 2.0 um andis optimized to produced optimal combination of resistive and acousticlosses. The thickness of the top and bottom electrodes range between 250Å and 2500 Å and the metal consists of a refractory metal with highacoustic velocity and low resistivity. The resonators are “passivated”with a dielectric (not shown in FIGS. 63A-63C) consisting of a nitrideand or an oxide and whose range is between 100 Å and 2000 Å. Thedielectric layer is used to adjust resonator resonance frequency. Extracare is taken to reduce the metal resistivity between adjacentresonators on a metal layer called the interconnect metal. The thicknessof the interconnect metal ranges between 500 Å and 5 um. The resonatorscontain at least one air cavity interface in the case of SMRs and twoair cavity interfaces in the case of FBARs and XBAWs. The shape of theresonators selected come from asymmetrical shapes including ellipses,rectangles, and polygons. Further, the resonators contain reflectingfeatures near the resonator edge on one or both sides of the resonator.

The RF filter circuit can comprise various circuit topologies, includingmodified lattice (“I”) 6401, lattice (“II”) 6402, and ladder (“III”)6403 circuit configurations, as shown in, and described above withreference to, FIGS. 64A, 64B, and 64C, respectively. In an example, thepresent invention provides an RF filter circuit device in a ladderconfiguration. The device can include an input port, a first nodecoupled to the input port, a first resonator coupled between the firstnode and the input port. A second node is coupled to the first node anda second resonator is coupled between the first node and the secondnode. A third node is coupled to the second node and a third resonatoris coupled between the second node and the third node. A fourth node iscoupled to the third node and a fourth resonator is coupled between thethird node and the output port. Further, an output port is coupled tothe fourth node. Those of ordinary skill in the art will recognize othervariations, modifications, and alternatives.

Each of the first, second, third, and fourth resonators can include acapacitor device. Each such capacitor device can include a substratemember, which has a cavity region and an upper surface region contiguouswith an opening in the first cavity region. Each capacitor device caninclude a bottom electrode within a portion of the cavity region and apiezoelectric material overlying the upper surface region and the bottomelectrode. Also, each capacitor device can include a top electrodeoverlying the single crystal material and the bottom electrode, as wellas an insulating material overlying the top electrode and configuredwith a thickness to tune the resonator.

The device also includes a serial configuration includes the input port,the first node, the first resonator, the second node, the secondresonator, the third node, the third resonator, the fourth resonator,the fourth node, and the output port. A separate shunt configurationresonator is coupled to each of the first, second, third, fourth nodes.A parallel configuration includes the first, second, third, and fourthshunt configuration resonators. Further, a circuit response can beconfigured between the input port and the output port and configuredfrom the serial configuration and the parallel configuration to achievea transmission loss from a pass-band having a characteristic frequencycentered around 5.2 GHz and having a bandwidth from 5.170 GHz to 5.330GHz such that the characteristic frequency centered around 5.2 GHz istuned from a lower frequency ranging from about 4 GHz to 5.1 GHz.

In a specific example, the first, second, third, and fourthpiezoelectric materials are each essentially a single crystal aluminumnitride bearing material or aluminum scandium nitride bearing material,a single crystal gallium nitride bearing material or gallium aluminumbearing material, or the like. In another specific embodiment, thesepiezoelectric materials each comprise a polycrystalline aluminum nitridebearing material or aluminum scandium bearing material, or apolycrystalline gallium nitride bearing material or gallium aluminumbearing material, or the like.

In a specific example, the serial configuration forms a resonanceprofile and an anti-resonance profile. The parallel configuration alsoforms a resonance profile and an anti-resonance profile. These profilesare such that the resonance profile from the serial configuration isoff-set with the anti-resonance profile of the parallel configuration toform the pass-band.

In a specific example, the pass-band is characterized by a band edge oneach side of the pass-band and having an amplitude difference rangingfrom 10 dB to 60 dB. The pass-band has a pair of band edges; each ofwhich has a transition region from the pass-band to a stop band suchthat the transition region is no greater than 250 MHz. In anotherexample, pass-band can include a pair of band edges and each of theseband edges can have a transition region from the pass-band to a stopband such that the transition region ranges from 5 MHz to 250 MHz.

In a specific example, each of the first, second, third, and fourthinsulating materials comprises a silicon nitride bearing material or anoxide bearing material configured with a silicon nitride material anoxide bearing material.

In a specific example, the present device can further include severalfeatures. The device can further include a rejection band at a frequencygreater than the pass-band. This rejection band can range from 5.490 GHzto 5.835 GHz. The device can further include an insertion loss of 2.1 dBand an amplitude variation characterizing the pass-band of 0.7 dB. Also,the device can include an attenuation of up to 40 dB for a frequencyrange of 1 GHz to 5 GHz or an attenuation of up to 48 dB for a frequencyrange of 5.9 GHz to 11 GHz. The device can further include a return losscharacterizing the pass-band of up to 15 dB and the device can beoperable from −40 Degrees Celsius to 85 Degrees Celsius. The device canfurther include a maximum power within the pass-band of 30 dBm or 1Watt. Further, the pass-band can be configured for a U-NII-1+U-NII-2Abands and for an IEEE 802.11a channel plan.

In a specific example, the present device can be configured as a bulkacoustic wave (BAW) filter device. Each of the first, second, third, andfourth resonators can be a BAW resonator. Similarly, each of the first,second, third, and fourth shunt resonators can be BAW resonators. Thepresent device can further include one or more additional resonatordevices numbered from N to M, where N is four and M is twenty.Similarly, the present device can further include one or more additionalshunt resonator devices numbered from N to M, where N is four and M istwenty.

In an example, the present invention provides an RF circuit device in alattice configuration. The device can include a differential input port,a top serial configuration, a bottom serial configuration, a firstlattice configuration, a second lattice configuration, and adifferential output port. The top serial configuration can include afirst top node, a second top node, and a third top node. A first topresonator can be coupled between the first top node and the second topnode, while a second top resonator can be coupled between the second topnode and the third top node. Similarly, the bottom serial configurationcan include a first bottom node, a second bottom node, and a thirdbottom node. A first bottom resonator can be coupled between the firstbottom node and the second bottom node, while a second bottom resonatorcan be coupled between the second bottom node and the third bottom node.

In an example, the first lattice configuration includes a first shuntresonator cross-coupled with a second shunt resonator and coupledbetween the first top resonator of the top serial configuration and thefirst bottom resonator of the bottom serial configuration. Similarly,the second lattice configuration can include a first shunt resonatorcross-coupled with a second shunt resonator and coupled between thesecond top resonator of the top serial configuration and the secondbottom resonator of the bottom serial configuration. The top serialconfiguration and the bottom serial configuration can each be coupled toboth the differential input port and the differential output port.

In a specific example, the device further includes a first balun coupledto the differential input port and a second balun coupled to thedifferential output port. The device can further include an inductordevice coupled between the differential input and output ports. In aspecific example, the device can further include a first inductor devicecoupled between the first top node of the top serial configuration andthe first bottom node of the bottom serial configuration; a secondinductor device coupled between the second top node of the top serialconfiguration and the second bottom node of the bottom serialconfiguration; and a third inductor device coupled between the third topnode of the top serial configuration and the third bottom node of thebottom serial configuration.

The packaging approach includes but is not limited to wafer levelpackaging (WLP), WLP-plus-cap wafer approach, flip-chip, chip and bondwire, as shown in, and described above with reference to FIGS. 65A, 65B,and 66A. One or more RF filter chips and one or more filter bands can bepackaged within the same housing configuration. Each RF filter bandwithin the package can include one or more resonator filter chips andpassive elements (capacitors, inductors) can be used to tailor thebandwidth and frequency spectrum characteristic. For a tri-band Wi-Fisystem application, a package configuration including three RF filterbands, including the 2.4 GHz, 5.2 GHz, and 5.6 GHz band-pass solutionsis capable using the BAW RF filter technology. The 2.4 GHz filtersolution can be either surface acoustic wave (SAW) or BAW, whereas the5.2 GHz and 5.6 GHz bands are likely BAW given the high-frequencycapability of BAW.

In an example, the present filter passes frequencies in the range of5.17 to 5.33 GHz and rejects frequencies outside of this pass-band.Additional features of the 5.2 GHz acoustic wave filter circuit areprovided below. The circuit symbol which is used to reference the RFfilter building block is provided in FIG. 67 . The electricalperformance specifications of the 5.2 GHz filter are provided in FIG. 71and the pass-band performance of the filter is provided in FIG. 72 .

In various examples, the present filter can have certain features. Thedie configuration can be less than 2 mm×2 mm×0.5 mm; in a specificexample, the die configuration is typically less than 1 mm×1 mm×0.2 mm.The packaged device has an ultra-small form factor, such as a 2 mm×2.5mm×0.9 mm using a conventional chip and bond wire approach, shown inFIG. 65A. WLP package approaches can provide smaller form factors. In aspecific example, the device is configured with a single-ended 50-Ohmantenna, and transmitter/receiver (Tx/Rx) ports. The high rejection ofthe device enables coexistence with adjacent Wi-Fi UNIT bands. Thedevice is also be characterized by a high power rating (maximum+30 dBm),a low insertion loss pass-band filter with less than 2.5 dB transmissionloss, and performance over a temperature range from −40 degrees Celsiusto +85 degrees Celsius. Further, in a specific example, the device isRoHS (Restriction of Hazardous Substances) compliant and uses Pb-free(lead-free) packaging.

Referring back to FIG. 67 , which is a simplified circuit diagramillustrating a 2-port BAW RF filter circuit according to an example ofthe present invention. As shown, circuit 6700 includes a first port(“Port 1”) 6711, a second port (“Port 2”) 6712, and a filter 6720. Thefirst port represents a connection from a transmitter (TX) or received(RX) to the filter 6720 and the second port represents a filterconnection from the filter 6720 to an antenna (ANT).

FIG. 71 is a simplified table of filter parameters according to anexample of the present invention. As shown, table 6800 includeselectrical specifications for a 5.2 GHz RF resonator filter circuit. Thecircuit parameters are provided along with the specification units,minimum, along with typical and maximum specification values.

FIG. 72 is a simplified graph representing insertion loss over frequencyaccording to an example of the present invention. As shown, graph 6900represents a narrowband measured vs. modeled response for 5.2 GHz RFfilter using a ladder RF filter circuit configuration. The modeled curve6910 is the transmission loss (s21) predicted from a linear simulationtool incorporation non-linear, full 3-dimensional (3D) electromagnetic(EM) simulation. The measured curve 6920 is the s21 measured fromscattering parameters (s-parameters) taken from a network analyzer testsystem.

What is claimed is:
 1. An RF filter circuit device, the devicecomprising: an input port; a first node coupled to the input port; afirst resonator coupled between the first node and the input port, thefirst resonator comprising a first capacitor device, the first capacitordevice comprising a first substrate member, the first substrate memberhaving a first cavity region and a first upper surface region contiguouswith a first opening of the first cavity region, a first bottomelectrode within a portion of the first cavity region, a firstpiezoelectric material overlying the first upper surface region and thefirst bottom electrode, a first top electrode overlying the firstpiezoelectric material and overlying the first bottom electrode, and afirst insulating material overlying the first top electrode andconfigured with a first thickness to tune the first resonator; a secondnode coupled to the first node; a second resonator coupled between thefirst node and the second node, the second resonator comprising a secondcapacitor device, the second capacitor device comprising a secondsubstrate member, the second substrate member having a second cavityregion and a second upper surface region contiguous with a secondopening of the second cavity region, a second bottom electrode within aportion of the second cavity region, a second piezoelectric materialoverlying the second upper surface region and the second bottomelectrode, a second top electrode overlying the second piezoelectricmaterial and overlying the second bottom electrode, and a secondinsulating material overlying the second top electrode and configuredwith a second thickness to tune the second resonator; a third nodecoupled to the second node; a third resonator coupled between the secondnode and the third node, the third resonator comprising a thirdcapacitor device, the third capacitor device comprising a thirdsubstrate member, the third substrate member having a third cavityregion and a third upper surface region contiguous with a third openingof the third cavity region, a third bottom electrode within a portion ofthe third cavity region, a third piezoelectric material overlying thethird upper surface region and the third bottom electrode, a third topelectrode overlying the third piezoelectric material and overlying thethird bottom electrode, and a third insulating material overlying thethird top electrode and configured with a third thickness to tune thethird resonator; a fourth node coupled to the third node; a fourthresonator coupled between the third node and the fourth node, the fourthresonator comprising a fourth capacitor device, the fourth capacitordevice comprising a fourth substrate member, the fourth substrate memberhaving a fourth cavity region and a fourth upper surface regioncontiguous with a fourth opening of the fourth cavity region, a fourthbottom electrode within a portion of the fourth cavity region, a fourthpiezoelectric material overlying the fourth upper surface region and thefourth bottom electrode, a fourth top electrode overlying the fourthpiezoelectric material and overlying the fourth bottom electrode, and afourth insulating material overlying the fourth top electrode andconfigured with a fourth thickness to tune the fourth resonator; anoutput port coupled to the fourth node; a serial configurationcomprising the input port, the first node, the first resonator, thesecond node, the second resonator, the third node, the third resonator,the fourth resonator, the fourth node, and the output port; a firstshunt configuration resonator coupled to the first node; a second shuntconfiguration resonator coupled to the second node; a third shuntconfiguration resonator coupled to the third node; and a fourth shuntconfiguration resonator coupled to the fourth node; a parallelconfiguration comprising the first shunt configuration resonator, thesecond shunt configuration resonator, the third shunt configurationresonator, and the fourth shunt configuration resonator; and a circuitresponse between the input port and the output port and configured fromthe serial configuration and the parallel configuration to achieve atransmission loss from a pass band having a characteristic frequencycentered around 3.625 GHz and having a bandwidth from 3.55 GHz to 3.7GHz such that the characteristic frequency centered around 3.625 GHz istuned from a lower frequency ranging from about 2.9 GHz to 3.5 GHz. 2.The device of claim 1 wherein the first piezoelectric material, thesecond piezoelectric material, the third piezoelectric material, and thefourth piezoelectric are each an essentially single crystal aluminumnitride (AlN) bearing material, an essentially single crystal aluminumscandium nitride (AlScN) bearing material, or an essentially singlecrystal magnesium hafnium aluminum nitride (MgHfAlN) material.
 3. Thedevice of claim 1 wherein the first piezoelectric material, the secondpiezoelectric material, the third piezoelectric material, and the fourthpiezoelectric material are each comprise a polycrystalline aluminumnitride (AlN) bearing material, a polycrystalline aluminum scandiumnitride (AlScN) bearing material, or a polycrystalline magnesium hafniumaluminum nitride (MgHfAlN) material.
 4. The device of claim 1 whereinthe first piezoelectric material, the second piezoelectric material, thethird piezoelectric material, and the fourth piezoelectric material areeach an essentially single crystal gallium nitride (GaN) bearingmaterial or an essentially single crystal gallium aluminum nitride(GaAlN) bearing material.
 5. The device of claim 1 wherein the firstpiezoelectric material, the second piezoelectric material, the thirdpiezoelectric material, and the fourth piezoelectric material are eachcomprise a polycrystalline gallium nitride (GaN) bearing material or apolycrystalline gallium aluminum nitride (GaAlN) bearing material. 6.The device of claim 1 wherein the serial configuration forms a resonanceprofile and an anti-resonance profile; and the parallel configurationforms a resonance profile and an anti-resonance profile such that theresonance profile from the serial configuration is off-set with theanti-resonance profile of the parallel configuration to form thepass-band.
 7. The device of claim 1 wherein the pass band ischaracterized by a band edge on each side of the pass-band having anamplitude difference ranging from 10 dB to 60 dB.
 8. The device of claim1 wherein each of the first insulating material, the second insulatingmaterial, the third insulating material, and the fourth insulatingmaterial comprises a silicon nitride bearing material or an oxidebearing material configured with a silicon nitride material or an oxidebearing material.
 9. The device of claim 1 wherein the pass-band has apair of band edges, each of the band edges having a transition regionfrom the pass-band to a stop band such that the transition region is nogreater than 250 MHz.
 10. The device of claim 1 wherein the pass-bandhas a pair of band edges, each of the band edges having a transitionregion from the pass band to a stop band such that the transition regionranges from 5 MHz to 250 MHz.
 11. The device of claim 1 furthercomprising a stop band rejecting signals below 3.55 GHz and above 3.7GHz.
 12. The device of claim 1 further comprising an insertion loss ofless than 2.5 dB.
 13. The device of claim 1 further comprising a maximumamplitude variation characterizing the pass-band of less than 1.5 dB.14. The device of claim 1 further comprising one or more additionalshunt resonator devices numbered from N to M, where N is four and M istwenty.
 15. The device of claim 1 further comprising a minimum returnloss characterizing the pass-band of 10 dB.
 16. The device of claim 1wherein the device is operable from −40 Degrees Celsius to 85 DegreesCelsius.
 17. The device of claim 1 further comprising a microwavecharacteristic impedance of 50 Ohms.
 18. The device of claim 1 furthercomprising a maximum power handling capability within the pass-band of+27 dBm or 0.5 Watt.
 19. The device of claim 1 wherein the pass band isconfigured for 4.5G CBRS LTE applications.
 20. The device of claim 1being configured as a bulk acoustic wave (BAW) filter device; whereineach of the first resonator, the second resonator, the third resonator,and the fourth resonator is a bulk acoustic wave resonator; and whereineach of the first shunt resonator, the second shunt resonator, the thirdshunt resonator, and the fourth shunt resonator is a bulk acoustic waveresonator.
 21. The device of claim 1 further comprising one or moreadditional resonator devices numbered from N to M, where N is four and Mis twenty.
 22. An RF filter circuit device, the device comprising: aninput port; a first node coupled to the input port; a first resonatorcoupled between the first node and the input port, the first resonatorcomprising a first capacitor device, the first capacitor devicecomprising a first substrate member, the first substrate member having afirst cavity region and a first upper surface region contiguous with afirst opening of the first cavity region, a first bottom electrodewithin a portion of the first cavity region, a first piezoelectricmaterial overlying the first upper surface region and the first bottomelectrode, a first top electrode overlying the first piezoelectricmaterial and overlying the first bottom electrode, and a firstinsulating material overlying the first top electrode and configuredwith a first thickness to tune the first resonator; a second nodecoupled to the first node; a second resonator coupled between the firstnode and the second node, the second resonator comprising a secondcapacitor device, the second capacitor device comprising a secondsubstrate member, the second substrate member having a second cavityregion and a second upper surface region contiguous with a secondopening of the second cavity region, a second bottom electrode within aportion of the second cavity region, a second piezoelectric materialoverlying the second upper surface region and the second bottomelectrode, a second top electrode overlying the second piezoelectricmaterial and overlying the second bottom electrode, and a secondinsulating material overlying the second top electrode and configuredwith a second thickness to tune the second resonator; a third nodecoupled to the second node; a third resonator coupled between the secondnode and the third node, the third resonator comprising a thirdcapacitor device, the third capacitor device comprising a thirdsubstrate member, the third substrate member having a third cavityregion and a third upper surface region contiguous with a third openingof the third cavity region, a third bottom electrode within a portion ofthe third cavity region, a third piezoelectric material overlying thethird upper surface region and the third bottom electrode, a third topelectrode overlying the third piezoelectric material and overlying thethird bottom electrode, and a third insulating material overlying thethird top electrode and configured with a third thickness to tune thethird resonator; a fourth node coupled to the third node; a fourthresonator coupled between the third node and the fourth node, the fourthresonator comprising a fourth capacitor device, the fourth capacitordevice comprising a fourth substrate member, the fourth substrate memberhaving a fourth cavity region and a fourth upper surface regioncontiguous with a fourth opening of the fourth cavity region, a fourthbottom electrode within a portion of the fourth cavity region, a fourthpiezoelectric material overlying the fourth upper surface region and thefourth bottom electrode, a fourth top electrode overlying the fourthpiezoelectric material and overlying the fourth bottom electrode, and afourth insulating material overlying the fourth top electrode andconfigured with a fourth thickness to tune the fourth resonator; anoutput port coupled to the fourth node; a serial configurationcomprising the input port, the first node, the first resonator, thesecond node, the second resonator, the third node, the third resonator,the fourth resonator, the fourth node, and the output port; a firstshunt configuration resonator coupled to the first node; a second shuntconfiguration resonator coupled to the second node; a third shuntconfiguration resonator coupled to the third node; and a fourth shuntconfiguration resonator coupled to the fourth node; a parallelconfiguration comprising the first shunt configuration resonator, thesecond shunt configuration resonator, the third shunt configurationresonator, and the fourth shunt configuration resonator; and a circuitresponse between the input port and the output port and configured fromthe serial configuration and the parallel configuration to achieve atransmission loss from a pass band having a characteristic frequencycentered around 3.625 GHz and having a bandwidth from 3.55 GHz to 3.7GHz such that the characteristic frequency centered around 3.625 GHz istuned from a lower frequency ranging from about 2.9 GHz to 3.5 GHz, thedevice further comprising: a minimum attenuation of 40 dB for afrequency range of 700 MHz to 1000 MHz; a minimum attenuation of 45 dBfor a frequency range of 1900 MHz to 2400 MHz; a minimum attenuation of50 dB for a frequency range of 2400 MHz to 2500 MHz; a minimumattenuation of 45 dB for a frequency range of 2500 MHz to 3340 MHz; aminimum attenuation of 40 dB for a frequency range of 3340 MHz to 3450MHz; a minimum attenuation of 12 dB for a frequency range of 3450 MHz to3530 MHz; a minimum attenuation of 12 dB for a frequency range of 3720MHz to 3800 MHz; a minimum attenuation of 30 dB for a frequency range of3800 MHz to 3910 MHz; a minimum attenuation of 40 dB for a frequencyrange of 3910 MHz to 4200 MHz; and a minimum attenuation of 50 dB for afrequency range of 5100 MHz to 5900 MHz.